348 



GYMNOSPERMS 



it is convenient, for the sake of reference, to have some name for the 

 stages before the grov/ing sporophyte breaks through the base of the 

 egg. The term "proembryo" has long been used for this part of the 

 embryogeny. 



Lalcr embryogeny. — While stages in the development of the em- 

 bryo have been studied, often rather thoroughly, ever since the time 



Fig. 336. — Araucaria braziliensis: A, the proembryo fills the entire egg: the shaded 

 cells are the embryo proper; the cells above form the suspensor; and the cells below, the 

 protective cap; B, later stage; the protective cap at the left is being pushed ofif; many 

 of the cells above are "embryonal tubes." X1S3. — After Strasburger.*"" 



of HoFMEiSTER,^s9 investigations of later stages had been compara- 

 tively desultory, until Buchholz''^^^^ made a critical examination 

 of nearly all the genera of the order. With a new and ingenious tech- 

 nique, he was able to remove the embryos entire and uninjured. 

 With such preparations, many of them examined in the living condi- 

 tion, and all of them after critical staining, it was easier to observe 

 and safer to interpret, especially in the numerous cases of polyem- 

 bryony. More than one embryo is so common in the gymnosperms 

 that it might be called their most distinguishing characteristic (fig. 



