190 



STUDIES IN CRYPTOGAMS 



3;!9. Section through a receptacle of 

 Polytrichum commune, showing 

 paraphyses and antheridia. 



propriately, "moss flowers. 



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



the stem, thus protecting the delicate assimilating tissue. 



The antheridia and archegonia of polytrichum 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 pcriduL'lia or peri- 

 ch(etal 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 antlieridia 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 polytrichum when the re- 

 ceptacles have fulfilled their 



function the stem continues 



to grow from the center of 



the cup (Fig. 340, m). Tlie 



archegonia are borne in otlier 



receptacles on different plants. 



They are like the archegonia 



of marchantia except that they 



stand erect on the end of the 



branch. 



The sporogonium which 



develops from the fertilized 



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



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 



is entirely inclosed by a hairy 



cap, the calypira, h. The ealyptra is really the 



archegonium, which, for a time, increases in size 



340. Polytrichum commune; ^ A fertile plants, 

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



remnant of tho 

 to aceommodale 



