IV 



THE JUNGERMANNIACE.E 



97 



of the simplest character, consisting of a single layer of polygonal 

 cells containing numerous chloroplasts. 



The plants grow where they are exposed to alternate 

 wetting and drying up. They may at any stage become 

 completely dried up, and on being moistened will resume at 

 once their activity. In the dried condition, the species under 

 consideration often remains for several months without 



Fig. 42. — Porella Bolanderi (Aust.). A, Median longitudinal section of a vegetative axis ; B,' a 

 cross-section of the apex of a similar one, x 500 ; x, the apical cell ; h, hair ; d., dorsal surface'; 

 V, ventral surface. 



apparently being injured in the least, and this power is shared 

 to a considerable degree by most of the acrogynous forms, whose 

 favourite habitat is the trunks of trees. 



The apical growth of the stem is extremely regular, and as in 

 all the other acrogynous Hepaticae, the apical cell is a three-sided 

 pyramid (Fig. 42, A). In longitudinal section it is much deeper 

 than broad, and its outer face is almost flat. In cross-sections 

 (Fig. 42, B) it has the form of an isosceles triangle, the shorter 



H 



