4 8o BOTANY OF THE LIVING PLANT 



But light is shed upon it by the Psilotales, which of living plants appear to be 

 the nearest allies of the Psilophytales. Their prothallus and embryology have 

 now been observed. In them we see that the freedom of the sporophyte follows 

 simply and directly on decay of the prothallus. With such facts in view, the 

 relation of the Bryophyta to the Pteridophyta becomes more intelligible now 

 than it was before the discovery of the Psilophytales, or the completion of the 

 life-history of the Psilotales. For a more complete treatment of the Psilophy- 

 tales, see Primitive Land Plants, Chapters VII., VIII. 



