and its relation to that in the Animal Kingdom. 859 



what occurs in the tubes of the microspores, led Hofmeister to 

 the conjecture that spermatic filaments might also be produced 

 there*; but his own later researches, and those of Schachtf^ 

 have not confirmed this supposition. 



Conifers and CycADEiE (Gymnospermia). — IntheConiferse 

 the investigation of the formation of the embryo has not arrived 

 at satisfactory conclusions in all points J. But there exists evi- 

 dence to produce overwhelming probability that it originates from 

 a cell — a germinal vesicle, — with which the pollen-tube enters 

 into as intimate contact as in the rest of the Phancrogamia. 

 But the process of fecundation in Coniferse deviates strikingly in 

 two points. 



The first deviation is in the organization of the ovule. The 

 embryo-sac here becomes filled-up with endosperm, by cell- 

 formation around free nuclei and subsequent cell-division, before 

 the complete penetration of the pollen-tube through the nucleus 

 (which is clothed by a single integument). Certain of these 

 endosperm-cells (belonging to the second stratum, counting 

 down from the micropyle) expand, displacing the neighbom'ing 

 tissue, forming secondary embryo-sacs {corpuscula, R. Br.), and 

 subsequently, as 5-8 longish sacs, either lie immediately side 

 by side (Cupressinese) or remain separated by layers of unen- 

 larged endosperm-cells. That cell of the outermost layer of 

 endosperm-cells which covers the summit of each corpusculum, is 

 converted by crossing perpendicular walls into a I'osette of four 

 cells, between which the pollen-tube, after breaking through the 

 softened membrane of the (primary) embryo-sac, subsequently 

 penetrates, bulging out, either simply to apply itself upon the 

 outside of the corpusculum, or, by the absorption of the apex, to 

 advance some distance into the interior. 



About this time the corpusculum becomes filled up with deli- 

 cate cells (some of which already contain fom* daughter-cells), 

 swimming free, one of which immediately begins to enlarge, and 

 is subsequently found at the end of the corpusculum turned 



* Vergleich. Untersuch. p. 132 (1851). 



t ' nora,' 1854, p. 529. 



j Vide : Hofmeister, Vergleich. Unters. &c. Leipsic, 1851, p. 126 ; Ueb. 

 Befrucht. der Coniferen. Flora, 1854, p. 529. (Ann. Nat. Hist. 2 ser. xiv. 

 p. 429.) 



Schacht, Pflanzenzelle, p. 417 (1852); Beitr. z. Anat. u. Pliys. der Ge- 

 wacbs. Berlin, 1854, pp. 287, 324 ; Das ^likroskop. Berlin, 1855, p. 148. 



Geleznoff, Ann. des Sc. nat. 3 ser. xiv. p. 188 (1850). 



Pineau, Ann. des Sc. nat. 3 ser. xi. p. 83 (1849). 



Gottsche, Botanische Zeitung, 1845, pp. 3/8, 507. 



Mirbel et Spacli, Ann. des Sc. nat. 2 ser. xx. p. 257 (1843). 



Rob. Brown, Ann. des Sc. nat. 2 ser. xx. p. 193 (1843); Ann. Nat. Hist, 

 xiii. p. 368 (read at tbe meeting of the British Association at Edinburgh in 

 Aug\ist 1834). 



