72 



EMBRYOGENESIS IN PLANTS 



primary importance, but the actual working of the system is still very 

 obscure. 



The filamentous type of embryonic development is also well seen in 

 Geothallus and Riella. The presence of chloroplasts in the sporophytes 

 of some of these Hepaticae indicates that they have some capacity for 

 self-nutrition. Studhalter (1938) has shown that when young sporo- 

 phytes of Sphaerocarpus texanus and RielJa americana were excised and 

 cultured in water, they continued their normal development and reached 

 maturity through their own photosynthetic activity. 



HEPATICAE — JUNGERMANNIALES 



In the Jungermanniales the embryogeny is typically filamentous in 

 its early stages, e.g. Aneura, Fossombronia, and many others. Fig. 15. 

 The zygote typically enlarges, elongates and becomes divided by several 



Fig. 15. Embryogeny in Jungermanniales 



A-D, Fossombronia longiseta. A, Young embryo in I.s. showing the first and 

 second walls, I-I, 11,11. B, C, Transverse and longitudinal sections of an older 

 embryo. D, An older embryo, showing the beginning of the archesporial differen- 

 tiation ( X 525 ; after Campbell). E, F, Porella bolanderi. Embryos in longitudinal 

 section ( x 525 ; after Campbell). G-J, FniUama dilatata. Embryos in longitudinal 

 section (x 300). K, Symphyogyna, Embryo. L, Blasia, Embryo. M, Pellia caly- 

 cina. Young gametophyte plant from spore, showing characteristic segmentation 

 pattern (x 420). (G-M after Lei tgeb). 



