DIV. I 



BRYOPHYTA 



481 



columella, while in the Bryales (Fig. 458) it constitutes an open cylinder around 

 the columella. The elongated embryo is composed of segments which in the 

 Sphagnales arise by transverse division of the zygote and in other Mosses are cut 



F I<; . 440. Development of the sporogonium of the Moss, Funaria hygrometrica. A, B, Longitudinal 

 sections showing first stages in the development from the zygote s, apical cell. C-E, Transverse 

 sections: C, division into enduthecium (e) and amphithecium (a); D, further divided stage; 

 E, older sporogonium, in the endothecium of which the outermost layer is distinct as the 

 archesporium (or) from the columella (c> (After CAMPBELL.) 



off from a two-sided apical cell. In each transverse segment a longitudinal 

 division follows, and in the resulting quadrants there is a separation of outer cells 

 (amphithecium) from internal 

 cells (endothecium) (Fig. 440). 

 In the Sphagnales only, the 

 archesporium arises as the 

 innermost layer of the amphi- 

 thecium ; in all other Mosses 

 it is the outermost layer of the 

 endothecium. It gives rise 

 exclusively to spores, no sterile 

 cells being formed (Fig. 441). 



The Bryophyta are char- 

 acterised by a great power of 

 regeneration from cut portions 

 of all the organs. Vegetative 

 reproduction by means of 

 gemmae, etc., is widespread ; 

 they arise on the thallus, on 

 stems, on leaves, and on the 

 protonema in a great variety of ways, becoming separated later ( w ). 



There are difficulties in the way of the phylogenetic derivation of the Bryophyta 

 from any definite group of Algae. Fetween the Bryophytes on the one hand, and 



2 l 



--, 

 - 



B 



FIG. 441. Funaria, hygrometrica. Transverse section 

 through the archesporium (A, su), and the groups of still 

 connected spore -mother -cells derived from it (B, sm). 

 (After GOF.BEL.) 



