POLYTRICHUM THE SPOROGONIUM 185 



2. A band of brown scierenchyma, which graduates internally 

 into 



3. A thin-walled parenchyma with large intercellular spaces, 

 and containing chlorophyll. 



4. Centrally is a strand of denser tissue without intercellular 

 spaces. 



XI. Cut median longitudinal sections of the base of the seta, 

 which is inserted on the apex of the Moss-plant or oophyte : 

 mount as before, and note in the upper part of the seta the 

 superficial layer, brown scierenchyma, thin-walled parenchyma, 

 and central strand, as above described. Following the seta 

 down to the base, it will be seen that the cuticle and brown 

 scierenchyma stop short, and are replaced by thin-walled 

 parenchyma with plentiful protoplasm ; this tissue of the 

 sporophyte is in close connection with the inner surface of 

 the vaginula, which belongs to the oophyte generation. With 

 this close physiological connection of the sporophyte and 

 oophyte in the Moss compare the connection by means of the 

 foot in Ferns. 



XII. Passing now to the apex of the sporogonium of Polytri- 

 chum, remove the calyptra : mount it in water or weak glycerine, 

 and examine under a low power. It consists externally of 

 dry, branched, hypha-like filaments, loosely matted together : 

 the neck of the archegonium may often be recognized at its 

 extreme apex. Open the calyptra with needles in a drop of 

 water on a slide, and observe the firm inner cap the calyptra 

 proper which is covered externally by the hairy indumentum : 

 the latter is the result of outgrowth of superficial cells of the 

 calyptra. 



XIII. After having noted the external form of the capsule, 

 and of its operculum, transverse and longitudinal sections should 

 be cut. For this purpose it will be well to select young specimens, 

 in which the capsule has not attained more than half its full 

 girth : after hardening in alcohol they may be embedded in 

 paraffin, or held in pith, and the sections be cut : mount in gly- 

 cerine or in glycerine jelly. 



Taking first transverse sections cut from the middle of the 

 capsule, examine them under a low power and observe the 



