214 MOSSES AND FERNS CHAP. 



much in diameter at the base, where it is widened out like a 

 bell, and far exceeds in diameter the enclosed embryo. Above 

 it is narrow and lies close to the embryo. After a time the 

 embryo grows more rapidly in length than the calyptra, which 

 then is torn away by a circular rent about its base, and is 

 raised on top of the elongating sporogonium. The lower por- 

 tion remains delicate and nearly colourless, but the upper part 

 has its cells thick-walled and dark-brown in colour (Fig. 114, 

 C). Tipping the whole is the persistent dark-brown neck of 

 the archegonium. 



CLASSIFICATION OF THE BRYALES 

 CleistocarpcB 



The simplest of the Bryales are the Cleistocarpce or those 

 in which there is no operculum developed, and in consequence 

 the capsule opens irregularly. If Archidium is removed from 

 this group the simplest form known is Ephemerum. In this 

 genus, from a highly-developed filamentous protonema are pro- 

 duced the extremely reduced gametophores. According to 

 Muller, (2) who has studied the life-history of this genus, 

 both male and female branches arise from the same protonema, 

 and are only distinguishable by the smaller size of the former. 

 The axis of the branch is scarcely at all elongated, and the leaves 

 therefore appear close together. The sexual organs corre- 

 spond closely in origin and structure to the other Bryales. The 

 development of the sporogonium in its early phases is also the 

 same, and the differences only appear at a late stage. The 

 separation of endothecium and amphithecium is apparently ex- 

 actly the same as in other Bryales, and from the former is de- 

 rived the archesporium, which like that of Funaria has the form 

 of a hollow cylinder through which the columella passes. Be- 

 tween the outer spore-sac and the wall of the sporogonium an 

 intercellular space is also formed, but the separation of the cells 

 is complete, and there are no filaments connecting the spore-sac 

 and the sporogonium wall as in Funaria. The cells of the 

 archesporium are few in number and correspondingly large 

 (Fig 115, E), and before the division into the spores takes 

 place all the central tissue of the columella is absorbed, and 

 the spore mother cells occupy the whole central space, where 

 the division of the spores is completed, and at maturity the 



