432 HOFMEISTER, ON 



considerably in breadth (PL LXV, figs. 7, 8). In Juni- 

 perus also all the numerous young embryos usually mis- 

 carry, except one. 



The stages of development of the embryos of the Co- 

 niferse which follow next after the impregnation of the 

 germinal vesicle, are passed through with just as much 

 rapidity as contemporaneity. A very short time, scarcely 

 twenty-four hours, elapses between the arrival of the 

 end of the pollen-tube at the upper end of the corpus- 

 culum of the Abietinese, and the formation of the four- 

 celled compound pro-embryo at its base; and these 

 processes of development occur almost contemporaneously 

 in all ovules of all trees of the same species growing 

 under similar circumstances. Thus in J 854 I found 

 that on the 22nd of June, near Leipzig, no single pollen- 

 tube of Pinus sylvestris had reached a corpusculum ; 

 whereas only three days later, on the 25th of June, there 

 was only one amongst several hundreds of impregnated 

 corpuscula which I examined, whose impregnated ger- 

 minal vesicle was not already divided into four cells. In 

 Taxus and the Juniperineae the contemporaneity of the 

 development is less complete ; here we find different stages 

 of development extending over about eight days, consist- 

 ing of germinal vesicles unimpregnated, impregnated and 

 unicellular, or impregnated and multicellular, all near one 

 another. 



Robert Brown* was the discoverer of the poly-embryony 

 of the Coniferse. In a later treatisef (1834) he pointed 

 out the origin of the pro-embryo in large cells of the en- 

 dosperm, to which he gave the name of corpuscula. Corda} 

 first proved that the pollen-tubes penetrate into the in- 

 terior of the corpuscula. Schleiden, in 1843, gave the 

 first accurate account of the nature of the pro- embryo. As 

 many subsequent observers have done, he mistook the 



* 'Ann. d. Sc.' 1st ser., vol. viii, p. 211. 



f 'Ann. d. Sc' 2nd ser., vol. xx, p. 193. 



% ' Nova Acta/ vol. xvii, p. 599. Upon other points this work is of no 

 use. 



' Grundziige,' 1st edn., vol. ii, p. 375. R. Brown's account of the young 

 pro-embryo is incomplete. He figures (1. c, vol. xx, pi. v, fig. 9) a pro-embryo 

 whose smaller terminal growing cells arc torn off. 



