482 SUMMARY OF CURRENT RESEARCHES RELATING TO 



sac, there is nothing to distinguish the oosphere from the other nuclei. 

 The antherozoids, when entering the embryo-sac, are elongated usually 

 curved nuclei, but are not coiled. As in Lilium, Fritillaria, and Endy- 

 rnion, the first division of the ovum-cell which forms the embryo is 

 always preceded by that of the impregnated secondary nucleus which 

 gives birth to the endosperm. 



Fertilisation in the Coniferse.* — Z. Wojcicki gives the following as 

 the results of his observations on Larix dahurica. In the pollen-tube 

 are two generative cells and two nuclei, that of the pollen-tube and that 

 of the posterior absorbed cell, which both enter the oosphere. The 

 protoplasm of the generative cells soon coalesces with that of the oosphere. 

 The larger of the two generative nuclei forces itself into the ovum- 

 nucleus, and coalesces completely with it. Karyokinetic division then 

 takes place in the nucleus of the embryo, in which only its central part 

 participates ; the relatively small spindle, with the chromosomes, lies in 

 the interior of the membraneless nucleus, surrounded by a broad zone of 

 nuclear substance, which may be recognised as a delicate network of 

 small feebly trainable granules. The second stage of division takes 

 place within these remains of nuclear substance, which appear sub- 

 sequently to fuse with the adjacent zone of denser protoplasm. After 

 the complete development of the four daughter-nuclei, they sink, together 

 with the surrounding zone of protoplasm, to the base of the oosphere, 

 forming there, by threefold division, four groups, each of four nuclei. 

 The protoplasm of the three lower groups, which represent the embryo, 

 is divided off by cell-walls, while the nuclei of the iippermost group 

 remain free. The second sperm-nucleus can still be recognised at this 

 stage in the upper part of the oosphere. 



Endosperm of Sequoia.f — Herr W. Arnold describes the develop- 

 ment of the endosperm in Sequoia sempervirens, comparing it with that 

 in Gnetum on the one hand, and with that in typical conifers on the other 

 hand ; from which he draws the conclusion that Sequoia is a connecting 

 link between Gnetum and the Angiosperms on the one hand, and between 

 the Gymnosperms and the Archegoniatse on the other hand. 



The form of the embryo-sac is very variable. At a very early period 

 the protoplasm forms a parietal layer through which numerous nuclei 

 are distributed, enclosing a large vacuole ; the nuclei multiply in the 

 ordinary karyokinetic way. The layer of jm>toplasui increases in thick- 

 ness, and accumulates especially at the lower end of the embryo-sac. In 

 the upper and lower portions of the embryo-sac a formation of endosperm 

 now takes place by free-cell-formation ; while in the central portion it is 

 formed in quite a different way. Kere a large vacuole still remains 

 after the increase of the protoplasm in the upper and lower portions, the 

 vacuole being surrounded on all sides by protoplasm in which a number 

 of nuclei are imbedded. In this protoplasm are found numerous vesicles 

 (Alveolen), as in other Coniferae, one being formed round each nucleus, 

 each ultimately breaking up into several cells by the division of its 

 nucleus. The tissue formed by free-cell-formation in the lower portion 

 of the embryo-sac serves ouly as a store of nutriment for the future 



- In Russian ; Warscliau, 1899, 2 pis. See Bot. Ztg., Iviii. (1900) 2" Alt., p. 39. 

 t Bull. Soc. Imp. Nat. Moscou, 1899 (1900) pp. 329-41 (2 pis.). Of. this Journal, 

 189(3, p. 617. 



