24 PRACTICAL BOTANY. 



that the lowest cell of each tier projects into the cavity 

 of the " stoma," so that the channel at that point 

 presents a stellate appearance in surface view. 



Sections should also be cut from the thallus of Lunularia, 

 wherein it will be found that the stomata do not correspond to 

 the above description, but are of a simpler type, and it is well 

 to compare the structure in Lunularia with that in Marchantia. 



V. Remove a number of the rhizoids : mount them 

 in water or glycerine, and examine under a low power : 

 two types of these elongated unbranched hairs may be 

 recognised 



a. Those with smooth walls : these are the more 

 numerous : 



I. Those with peg-like projections of the wall into 

 the cavity of the hair : these projections are arranged 

 in a more or less clearly spiral manner, and they may 

 not unfrequentJy be seen to be branched irregularly : 

 the protoplasmic contents are very scanty. 



VI. Avoiding, 'as before, both the cups with gemmae, and 

 the sexual branches, cut from material hardened in spirit fine 

 median longitudinal sections of the thallus, so as to include the 

 depressed apex : mount in glycerine, and examine under a high 

 power. 



In the older part of the section the structure of the thallus 

 will be seen as above described : on approaching the apex, note 

 that the air-cavities are successively smaller, and the chlorophyll- 

 containing tissue gradually disappears. The thallus has a blunt 

 apex covered by numerous amphigastria, which thus protect it. 

 At the extreme organic apex may be seen a single wedge-shaped 

 cell, which is, however, only one of a series of initial cells of 

 like form, as may be ascertained on careful investigation by 



