4G6 



THE CANADIAN NATURALIST. 



[Dec. 



their chlorophyl, those at the base are empty, hyaline, and elon- 

 gated ; in a few mosses the chlorophyl is wanting, and hence they 

 have a white aspect, as in the family Leucobryaceae. 



Occasionally the basal wing of the leaf is occupied by cells, 

 which differ from the rest, being enlarged or deeply coloured, and 

 the presence or absence of these alar cells has been conveniently 

 used by Prof. 8chimper to divide the great genus Dicranum into 

 two sections. When the cell-ends join by horizontal walls, 

 they are termed Parenchymatous, and in one form of these, the cell 

 walls are thickened, and the cell proper reduced to a mere point, 

 producing the dotted areolatioDS of Grimmiaceae and others (figs. 

 5, 6). When the cell ends are pointed, we have rhombic areola, 



Fig. 5. Areolation of 

 Pottia truncata. 



Fig. 6. Areolation of 

 Grimmia apocarpa. 



and these are termed Prosenchymatous, as in Bryum (figs. 7, 8). 

 I must add that occasionally stipuliform organs occur intermixed 

 with the stem leaves, as in Hi/pnum mplluscum ; these are named 

 Paraphyllia. 



An anomalous form of leaf occurs in the genus Fissidens, in 

 which it appears to be vertical, and split into two laminae for a 

 part of its length. This split portion is, however, the true leaf, 

 but the nerve and one wing have taken upon themselves extra- 

 ordinary development, and there is also a lamina formed along 

 the back of the nerve, these additional parts being named the 

 apical and dorsal laminae (fig. 9). 



The reproductive organs. — It is now satisfactorily deter- 

 mined that these are of two kinds, male and female, and unless they 

 occur near each other, the fruit is not produced; as an instance, 

 I may refer to Fissidens grandifrons, of which male plants only 

 have been found in Europe, female only in America, hence the 

 fruit is unknown. 



Hedwig was the first who pointed out the nature of these 



