and on the thickness of the pit-closing membrane; and in many cases the only evidence of such perforating threads is afforded by the general staining of the membrane. Every transition occurs between clearly defined threads in the substance of the closing membrane, and the mere staining of that structure as a whole.

The author has found in all pitted tissues a pit-closing membrane which is made evident by staining thin sections with iodine and mounting in chlor-zinc-iod, and has never seen open pits. The continuity of the protoplasm is always established by means of fine threads arranged in a sieve-structure, and not by means of comparatively large processes which the occurrence of open pits would necessitate.

A continuity of the protoplasm between adjacent cells occurs in Dionaea muscipula, and is especially pronounced in the most central layers of parenchymatous cells. The parenchyma-cells of the petioles of certain plants, which are often thick-walled and conspicuously pitted, afford favourable material for investigation. In Aucuba japonica and Prunus lauro-cerasus distinct threads can be made out crossing the pit-closing membrane. In Ilex Aquifolium there is a doubtful striation, and in others examined a mere coloration of the pit-membrane.

The author believes the connection of cells with one another to be a universal phenomenon, and the functions of the filaments to be as follows:-In sieve-tubes and in endosperm-cells they make possible a transference of solid materials; but in ordinary cells their only purpose is to establish a communication of impulses from one part of the plant to another.

By means of the methods described Mr. Gardiner has examined the seeds of about 50 species of palms, as well as those of representatives of the orders Leguminosa, Rubiacea, Myrsineæ, Loganiaceæ, Hydrophyllaceae, Iridaceae, Amaryllidaceae, Dioscorea, Melanthacea, Liliaceae, Smilaces, and Phytelephasieæ, in all of which he found that the cells of the endosperm are placed in communication with one another by means of delicate threads traversing their walls.

Living and Dead Protoplasm.*-O. Loew makes a final defence of his views as to the essential difference between living and dead protoplasm, and the aldehydic nature of the former. The facts relied on are mainly the following:-(1) the rise of temperature on the death of the cell; (2) the sudden setting in of an acid reaction; (3) the fact that living protoplasm does not precipitate any pigment, while dead protoplasm does. The author states that the substance described by Reinke under the name of plastin, is an impure albuminoid soluble with difficulty in dilute potassa; and that nuclein is also chiefly composed of an albuminoid combined with phosphoric acid.

Occurrence of Protoplasm in Intercellular Spaces.†-G. Berthold notices several instances of the occurrence of this phenomenon :-in

*Bot. Ztg., xlii. (1884) pp. 113-20, 129-32. Cf. this Journal, i. (1881) p. 906; ii. (1882) pp. 67, 361, 440, 522; iii. (1883) p. 225.

† Ber. Deutsch. Bot. Gesell, ii. (1884) p. 20.

the primary cortex of first-year twigs of Cornus mas, Ligustrum vulgare, and Staphylea pinnata; in the small intercellular spaces between the collenchymatous peripheral cells of the leaf-hinge of Epimedium alpinum and of the leaf-stalk of Pittosporum Tobira; in the primary cortex of Rhus glabra, &c. In order to detect this intercellular protoplasm, uninjured pieces of the plant must be laid in alcohol, or must be first hardened in potassium bichromate. One of the best objects is Ligustrum vulgare, where the small intercellular spaces of the young leaves of the winter-buds, as well as those between the young medullary cells, may be found to be filled with a protoplasmic substance.

Division of the Cell-nucleus.*-The following are the main results of a series of experiments on this subject by E. Heuser:

The only point which distinguishes the material of the nucleus from the surrounding protoplasm is that it consists to a large extent of nuclein. When at rest the substance of the nucleus consists of granules of various sizes imbedded in the nuclear hyaloplasm which has the form of a framework composed of strings. The granules do not all agree in chemical and physical properties. The nuclear hyaloplasm is surrounded by nuclear sap, apparently identical with the cell-sap, and is in continuous connection with the cyto-hyaloplasm through the membrane of the nucleus. The nuclear membrane consists of an extremely fine-meshed net of cyto-hyaloplasm, in which a few microsomes may be imbedded. This network is entered on one side by the delicate threads of cytoplasm, on the other side by the fine strings of the interior of the nucleus.

The nucleoli are larger collections of nuclear hyaloplasm, which serve as reservoirs for the substance of the nucleus, possibly in solution. The substance of the nucleus is divided, even while it still has the form of a ball, transversely into a number of loops. A further segmentation also occurs in the pollen-mother-cells of Tradescantia. The loops consist of nuclear substance, which, both in this condition and in that of rest, is surrounded by a sheath of hyaloplasm. These sheaths are still partially connected with one another after the transverse division of the substance of the nucleus, but afterwards only with the nuclear membrane. Immediately after the disappearance of this membrane, the threads of the hyaloplasmatic figure (the spindlefibres of Strasburger and the achromatic figure of Flemming) arise out of the sheaths of hyaloplasm by the addition of cyto-hyaloplasm.

The elements of the nuclear substance, before splitting longitudinally into the equatorial plate of Strasburger, are not distributed equally on both sides of the equator; there cannot therefore have been up to this time any "double decomposition" of the equatorial plate or bisection of the nucleus. To render possible the formation of two daughter-nuclei of equal size a further complete division of the nuclear substance must therefore take place. This is effected by longitudinal splitting and re-disposition of the elements under the influence of the hyaloplasm, which is applied as "spindle-fibres" to

*Bot. Centralbl., xvii. (1884) pp. 27-32, 57-9, 85-95, 117-28, 154–7 (2 pls.).

the ends of the separate rays which lie nearest the centre of the equatorial plane. The separate rays behave differently according to their position and surroundings.

After the rays of the daughter-plane have bent at their polar ends in the form of a hook, the fibres of hyaloplasm leave the pole, and appear again on the equatorial side of the rudiments of the daughter-nuclei as "connecting threads." While they are developing, the young daughter-nuclei assume the form of a turban, which favours the absorption of nutriment from the polar side by means of the "polar rays." In consequence of this the transformation of the ball of threads into the framework commences from the polar side. The successive processes of formation of the mother-nucleus are repeated in reversed succession after the longitudinal splitting of the rays.

Apical Cell of Phanerogams.*-P. Korschelt confirms the statement of Dingler that the cone of growth in flowering plants is developed from a single tetrahedral apical cell, by the separation of daughter-cells. This general law is derived from the observation not only of Gymnosperms (Pinus Abies, P. orientalis, P. canadensis, Taxodium distichum, and Ephedra vulgaris), but also of Angiosperms (Elodea canadensis, Lemna minor, Ceratophyllum submersum, and Myriophyllum verticillatum).

Nettle-fibre.+-J. Moeller has made a histological examination of the fibres of the common stinging nettle, Urtica dioica, with the following results:

The primary bast-bundles of the stem do not form a connected ring, and its fibres are mostly separated by intermediate parenchyma. The cortical parenchyma is not sclerenchymatous. At the base of the stem the fibres are mostly about 0.12 mm. in diameter; higher up they are thinner; but even at the summit they have a diameter of 0.04 mm. The thinnest fibres of the nettle are therefore as thick as the thickest of hemp. In consequence of their isolation they are seldom polygonal. At the commencement of the time of flowering, the fibres in the upper portion of the stem only are completely thickened; those in the lower part have still large cavities. There are no pore-canals. Fibres were measured 22 mm. in length; they are very irregular in form. They consist of nearly pure cellulose; their behaviour with cuoxam is characteristic. They swell with extraordinary rapidity from without inwards; a sharply differentiated internal layer resists the action for some minutes; but this is also at length dissolved; and, in addition to a small quantity of the contents of the fibres, a delicate network remains, the primary membranes of the parenchyma-cells which surrounded the fibres.

In the opinion of the writer, the want of secondary bast-bundles, and the difficulty of separating the fibres completely from the surrounding parenchyma, present insuperable difficulties in the way of

Ber. Deutsch. Bot. Gesell., i. (1883) pp. 472-7 (1 pl.).

+ Deutsch. Allg. Polytechn. Ztg., 1883. See Bot. Centralbl., xvii. (1884)

p. 53.

using the fibres of the nettle for technological purposes; and the same objections apply to Laportia pustulata, which has been attempted to be naturalized in Germany from North America.

Laticiferous Tissue of Manihot Glaziovii (Cearà Rubber).*-D. H. Scott describes the laticiferous tissue of Manihot Glaziovii, and states the result of his observations to be that in Manihot the laticiferous tubes are not cells as in the members of the order Euphorbiacea hitherto investigated, but vessels, agreeing in most points of distribution, structure, and development with those of the Cichoriacea.

At the same time this high development of the laticiferous system is not inconsistent with the presence of numerous large and welldeveloped sieve-tubes. Hence the prevalent views as to the mutual substitution of these two classes of organs are, to say the least, of limited application. Dr. Scott considers it probable that even within a comparatively narrow circle of relationship the development of laticiferous tissue has had more than one starting-point, and he is disposed to assume a distinct origin in the order Euphorbiacea for the laticiferous cells and for the laticiferous vessels.

Laticiferous Tissue of Hevea spruceana.†-D. H. Scott describes the laticiferous tissue in the stem of Hevea spruceana to be similar in its general distribution to that in Manihot, and though his observations are not yet complete, its structure seems likewise to take the form of laticiferous vessels and not cells.

Development of Root-hairs.-E. Mer has made a fresh series of observations on the conditions favourable for the development of roothairs, and retains his previous opinion, in opposition to the conclusions of Schwarz, that it is promoted by retardation of the growth of the root. If grains of lentil are made to germinate on the surface of water fixed on a float made of cork, the growth of the rootlets is at first slow. They grow either obliquely or horizontally, or even rise towards the surface of the water, and become covered with long hairs. As their length increases they are more governed by geotropism, and grow in a more vertical direction. The hairs with which they are covered then become gradually shorter. The seeds of the pea, oat, and wheat present similar phenomena. The rootlets which spring from the bulb-scales of the onion are generally destitute of hairs, whether developed in water, moist air, or the soil. But, if allowed to grow for a time in moist air, until their growth has become retarded, a tuft of hairs will make its appearance at the extremity of each.

Symmetry of Adventitious Roots.§-Adventitious roots may spring either from a node, in connection with a leaf or axillary bud, or from an internode. Nodal adventitious roots are classified by D. Clos as follows:

1. Latero-foliar. From the edge of a leaf, either on one side

Quart. Journ. Micr. Sci., xxiv. (1884) pp. 194–204 (1 pl.).

+ Ibid., pp. 205-7.

Comptes Rendus, xcviii. (1884) pp. 583-6. Cf. this Journal, ante, p. 79. § Ibid., xcvii. (1883) pp. 787-8.

(Sedum album, Berberis cretica) or from both sides (Aristolochia rotunda).

2. Subfoliar. Either a single one from the point of insertion of the leaf (Mühlenbeckia complexa), or several in a whorl (Houttuynia cordata).

3. Substipular. From the lower surface of the stipule (Modiola caroliniana).

4. Axillo-foliar. From the axils either of aërial leaves (Crassula perfossa) or of underground scale-leaves (Mahonia Aquifolium).

5. Axillo-stipular. From the axil of stipules (Urtica dioica).

6. Latero-gemmar. In connection with the axillary bud, either on one side (Calystegia sepium) or on both sides (Spirea sorbifolia); sometimes only from one of two opposite buds (Paronychia capitata).

7. Supragemmar. From immediately above the axillary bud (Lythrum Salicaria, Lysimachia verticillata).

8. Subgemmar. From below each bud (Equisetaceæ, Menispermum canadense).

Penetration of Branches of the Blackberry into the Soil.*—J. Wiesner finds that the winter-buds of species of Rubus growing in woods with creeping branches are drawn into the soil by the shortening of the roots which spring from the apex of the shoot. This shortening takes place in the roots of the zone above the growing region, and results from increase of turgidity, in consequence of which the growing part of the root lengthens. On the boundary of these two zones of the root which behave in opposite ways are the roothairs, which fix the root firmly into the ground by becoming closely attached to particles of soil. In consequence of this, the upper zone of the stem becomes shorter, and the apex and growing region of the root cannot be drawn out or injured. The traction on this lower part resulting from the shortening of the upper part, is, however, weakened by the fact that, under the conditions in which the upper apex of the root becomes shorter, the lower or growing region stretches. The traction caused by the shortening is exerted simply in dragging the apex of the root into the soil. The shoots which root at their apex become also thicker at their upper end, which could only result from a reversal of the stream of water and from a movement of the protoplasm in a direction opposite to the normal one.

Circumnutation and Twining of Stems.†-J. Baranetzki argues in favour of Schwendener's view that the twining of stems is due to circumnutation and geotropism, rejecting de Vries's theory of the influence of the weight of the terminal bud.

Vegetable Acids and their effect in producing Turgidity.‡— According to H. de Vries, organic acids are never absent from the growing parts of plants; they are the principal, and frequently the only causes of turgidity. They are not usually free, but most commonly

* SB. K. Akad. Wiss. Wien, lxxxvii. (1883) pp. 7-17.

+ Mém. Acad. Imp. Sci. St. Petersbourg, xxxi. See Bot. Ztg., xli. (1883) p. 855. Bot. Ztg., xli. (1883) pp. 849-54.