224 



MORPHOLOG V. 



479. Embryo. — In the plants which we liave si-lccted thus far for study, 

 the egg, immediately after fecundation, we recollect, passed into a resting 

 state, and was enclosed by a thick protecting wall. But in riccia, and in the 

 other plants of the group which we are now studying, this is not the case. 



Fig. 2S3. 



Archegiiniuni of riccia, showing neck, 

 venter, and the egg; arcliegonium is partly 

 surrounded by tiie tissue of the thallus. 

 (Riccia crystallina) 



Fig. 254. 

 Voung embryo (sporogoni- 

 uni) of riccia, witliin tlie venter 

 of the archegonium ; the latter 

 has now two layers of cells. 

 (Riccia crystallina, ) 



The egg, on the other hand, after acqitiring a thin wall, swells up and tills 

 the cavity of the venter. Then it divides by a cross wall into two cells. 

 These two grow, and divide again, antl so on tmtil there is formed a quite 

 large mass of cells rounded in form and still cootained in the venter of the 

 archegonium, which itself increases in size by the growth of the cells of the 

 wall. 



480. Sporogonium of riccia. — The fruit of riccia, whicli is 

 developed from the fertihzed egg ill the archegonium, forms a 

 rounded capsule still enclosed in the venter of the archegonium, 

 which grows also to provide space for it. Therefore a section 

 through the plant at this time, as ciescribed for the study 

 of the archegoniuiti, should show this capsule. The capsule 

 then is a rounded mass of cells developed from the egg. A sin- 

 gle outer layer of cells forms the wall, and therefore is sterile. 



