LIVERWORTS 125 



Plate IX. fig. 5, taken from the tree-growing 

 plant, the Elat-leaved Liverwort (Radula com- 

 planata). 



This leafy envelope, or cup, as I may for 

 convenience call it, is known in botanical lan- 

 guage as the colesule or perianth. 



Its form varies, to some extent, in different 

 species. Thus the one just alluded to is simple 

 and cup-like in appearance; the one drawn at 

 fig. 3 of the same plate is more pear-shaped, and 

 has the mouth much contracted in this case, 

 moreover, there are a number of small wart-like 

 excrescences on the sides which at once serve to 

 show that it belongs to that common tree-loving 

 plant, the Tubercled Liverwort (Frullania dila- 

 tata), already described (p. 111). In some cases, 

 again, the upper edge is strongly toothed, while 

 in others it is so much cut up, as almost to have 

 the appearance of having been slashed by some 

 sharp instrument, and numerous other similar 

 small differences will be found in other species. 

 Although this leafy cup, as already mentioned, 

 always contains within it some of the fruit- 

 bearing organs, yet these are not unfrequently 

 formed before the cup, and the latter subsequently 

 grows round them. The cup itself no doubt 

 fulfils the same functions as those served by the 

 perichoetial leaves in mosses, namely, to protect 

 the small and delicate reproductive organs, and 

 to retain moisture around them with a view to 



