280 



METHODS IN PLANT HISTOLOGY 



stages of some forms, like Riccia natans, they may be difficult to cut on 

 account of the secondary thickening of the capsule wall and the stub- 

 born exine of the mature spores. Great care must be taken to get 



Fig. 80. — Marchanlia polymorpha: A, section through archegonial head. X30. B, an arche- 

 gonium shortly before fertilization, showing egg, ventral canal cell, and 8 neck canal cells. X300. C, 

 egg after fertilization. X300. D, young embryo; the spores will come from the more deeply sh.aded 

 part; the lightly shaded part will produce the foot and seta. X300. E, nearly mature embryo with 

 foot (/), stalk (s), and remains of ruptured archegonium (a). X45. From Chamberlain's Elements 

 of Plant Science (McGraw-Hill Book Co., New York). 



