MOSSES 95 



a number of very minute leaf -like bodies, which, 

 however, are often so much divided as almost 

 to lose their leafy look. These are known as 

 par aphy Ilia, and it is thought that, just as the 

 paraphyses help to retain moisture round the 

 flowers (see page 37), so these tiny growths 

 perform a similar function for the stem and 

 leaves. A few, much magnified, taken from two 

 members of the Feather-moss tribe, are given in 

 Plate IV. figs. 20 and 21. 



Leaf-cells. Of late years more and more 

 reliance has been placed upon the size and 

 form of the leaf-cells as a means of differen- 

 tiating between the various species, and these 

 points, nay, even the varying degrees of thick- 

 ness of the cell walls, thus become matters 

 which cannot too early claim the patient and 

 careful attention of the student. Needless to say 

 that here the use of a microscope is imperative, 

 for it is only in comparatively few cases that the 

 cells are sufficiently large to be discernible at 

 all, with any degree of precision, by the use of 

 a hand lens alone, while the more minute details 

 would be invisible without a much higher magni- 

 fication than could be obtained with such means. 

 A few instances must suffice to indicate the 

 general features that call for notice; the finer 

 distinctions can only be appreciated after some 

 considerable acquaintance with the numerous forms 

 has made one more or less familiar with their 



