190 



STUDIES IN CKYPTOGAMS 



3.'!9. Section through a receptacle of 

 Polytriehum commune, showing 

 paraphyses and antheridia. 



propriately, "moss flowers." 



gins of the leaves roll inward, and the leaves fold closely against 



the stem, thus protecting the delicate assimilating tissue. 



The antheridia and archegonia of polytriehum are borne in groups 



at the ends of the branches on different plants (many mosses bear 



both organs on the same branch). They 

 are surrounded by involucres of charac- 

 teristic leaves termed perichcetia or peri - 

 chcetal leaves. Multicellular hairs known 

 as paraphyses are scattered among the 

 archegonia and antheridia. The invo- 

 lucres with the organs borne within 

 them are called receptacles or, less ap- 

 As in marchantia, the organs are very 



minute and must be highly magnified to be studied. 



The antheridia are borne in broad cup-like receptacles on the 



antheridial plants (Fig. 339). They are much like the antheridia of 



marchantia, but they stand free among the para- 

 physes and are not sunk in cavities. At maturity 



they burst and allow the sperm-cells or spermat- 



ozoids to escape. In polytriehum when the re- 

 ceptacles have fulfilled their 



function the stem continues 



to grow from the center of 



the cup (Fig. 340, m). The 



archegonia are borne in other 



receptacles on different plants. 



They are like the archegonia 



of marchantia'exceptthat they 



stand erect on the end of the 



branch. 



The sporogonium which 



develops from the fertilized 



egg is shown in Fig. 340, a, b. 



It consists of a long, brown 



stalk bearing the spore-case at 



its summit. The base of the 



stalk is embedded in the end 



of the moss stem by which 



it is nourished. The Capsule 340. Polytriehum commune; f, /. fertile plants, 



,. , . , , , . one on the left in fruit ; m, antheridial plant, 



is entirely inclosed by a hairy 



cap, the calyptra, b. The calyptra is really the remnant of the 



archegonium, which, for a time, increases in size to accommodate 



