ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 677 



The stratification of the cellulin-grains is concentric, around a 

 nucleus of denser substance ; they grow, however, to a considerable 

 size before any stratification is evident. Compound grains are not 

 uncommon. A common mode of multiplication is by a kind of 

 budding, not dissimilar to that of torula. 



"When the oospheres are formed out of the protoplasmic contents 

 of the oogonium, an unused residue remains behind, which is the sub- 

 stance out of which the cellulin-grains are subsequently developed. 

 This substance is morphologically identical with the " periplasm " of 

 the Peronosporese, out of which the exospore of the oospore is 

 formed. 



Experiments on the propagation ofAchlya seem to demonstrate that 

 these cellulin-grains belong to the Saprolegniete themselves, and not 

 to any Chytridiese or other parasites upon them. 



Protrusion of the Endosperm through the Micropyle.* — In 

 harmony with the observation of Treub respecting Avicennia officinalis, 

 E. Warming states that in JRJiizophora Mangle the endosperm also 

 projects beyond the micropyle, but only partially, the greater part 

 being still inclosed in the testa. The projecting portion has much 

 the appearance of an aril. 



Development of the Pollen of Juncacese and Cyperaceae.t — 



N. Wille describes the development of the pollen-grains of Juncacese 

 {Juncus glauctis, Luzula campestris, maxima, and pilosa) as differing 

 from the typical mode. The pollen mother-cells divide, as usual, 

 into four special mother-cells ; but the wall of these special mother- 

 cells does not, as is usually the case, become absorbed ; its outermost 

 layers cuticularize into an extine, except one spot at each corner of 

 the tetrahedron, where the pollen-tube subsequently emerges. True 

 pollen-grains are therefore wanting ; fertilization being effected by 

 the special mother-cells; one stage of the usual development is 

 suppressed. 



In the CyperaccEe (two species of Carex, Eleocharis palustris), the 

 departure from the ordinary development is still greater. In the free 

 pollen mother-cells no special mother-cells are formed ; their pre- 

 paration only is indicated by divisions of the nucleus ; the new nuclei 

 apparently again coalescing. The outermost layer of the wall of 

 the pollen mother-cells is metamorjjhosed into the extine. In the 

 Cyperaceae therefore the development of the pollen-grains stops short 

 at one stage earlier even than in the Juncaceae. 



Continuity of Protoplasm through Walls of Vegetable Cells.t — 

 W. Gardiner is inclined to come to the conclusion that it is extremely 

 probable that the communication between adjacent vegetable cells 

 does not only take place in the parenchymatous cells of pulvini, in 

 the phloem parenchyma cells, in the cells of endosperms, and in the 

 prosenchymatous bast-fibres, but is of much wider if not of universal 



* Bot. Ztg., xli. (1883) pp. 203-4. 



t Christ. Videnskab. Forhandl., 1882. See Bot. Centralbl., xiv. (1883) 

 p. 296. 



+ Proc. Eoy. Soc, xxxv. (1883) pp. 163-6. Cf. this Journal, ante, pp. 225, 

 52i. 



