SECT. I 



CRYPTOGAMS 



437 



dry atmosphere the leaves fold together, and thus protect the delicate lamellae 

 from excessive transpiration (i^*). 



The RHizoiDS (Fig. 383), each of which consists of a branched filament of cells, 

 spring from the base of the stem. In structure they resemble the protonenia, into 

 which they sometimes become converted, and then can give rise to new iloss plants. 



The SEXUAL ORGANS are always borne in groups at the apices 

 either of the main axes or of small, lateral branches, surrounded by 

 their upper leaves ; each group Avith its involucral leaves constituting 



em 



Fic. 378. — sphagnum fDiihriatinn : A, A shoot with four ripe sporogoiiia. Sphagnum acutifolitua : 

 B, Archegoniuin with the multici'llular embryo of the sporogonium em ; (', a young sporo- 

 gonium in longitudinal section ; ps, pseudopodiuni ; ca, archegonial wall or calyptra ; ah, neck of 

 archegoniuin ; spf, foot of sporogonium ; k, capsule ; co, columella ; spo, spore-sac with spores ; 

 E, ruptured antheridium with escaping spermatozoids ; F, single sperniatozoid, highly 

 magnilied. Sphagnum sqnarrosum : D, A lateral shoot with a terminal sporogonium ; ca, 

 ruptured calyptra ; (/, operculum. (After W. P. Schimper ; .-1, nat. size ; the other figures 

 magnified.) 



a receptacle. The antheridial and archegonial receptacles are some- 

 times inappropriately referred to as moss flowers, but they have 

 nothing in common with the true flowers of vascular plants ; the 

 involucral leaves, which frequently have a distinctive structure, are 

 also known as the perichaetium (Fig. 383). Between the sexual 

 organs there are usually present a number of multicellular hairs or 

 paraphyses. The moss plants may be monoecious, in Avhich case both 

 kinds of sexual organs are boine on the same plant either in the same 

 or different receptacles ; or dioecious, and then the antheridia and 



