THE BRYOPHYTA : HEPATICAE, THE LIVERWORTS 



411 



Neighbouring cells grow out among the Algae in the form of filaments. 

 Stomata of the same type as those found on the sporophyte, with two bean- 

 shaped guard cells and an open slit, occur on the lower, and also in places 

 on the upper, side of the thallus. As there is no organized epidermis, gaseous 

 diffusion into the tissues is not limited to these stomata, which probably 

 only serve as outlets to the intercellular slime passages, which permeate the 

 inner tissues. Their presence and their structure, which resembles closely 

 that found in higher plants, speak strongly for the view that Anthoceros is a 

 morphologically reduced rather than an advancing type. 



Antherozoids 



Stalk 



Fig. 394. — Atit/ioceros loevis. Section through an 

 antheridial cavity containing antheridia. 



In the sporophyte the stomata open into internal air spaces and are 

 apparently normal in function. 



The algal afhnity suggested by the presence of pyrenoids in Anthoceros 

 is borne out by the production of vegetative reproductive bodies, or gemmae, 

 which are produced on short stalks on the upper surface of the thallus in 

 A. glandnlosus. Occasionally marginal tubers may be formed, which can 

 survive periods of drought. They are developed from modified thallus 

 lobes and store fat and protein ; when detached thev function as organs 

 of vegetative propagation. 



The Antheridium 



The development of the antheridia is endogenous. A surface cell divides 

 horizontally, the inner half forming a group of antheridia, and the upper half 

 forming a roof over them. The inner cell divides again twice, vertically, 

 each of the four cells thus formed usually developing into an antheridium, 

 though sometimes only two or three develop (Fig. 394). The roof cell 



