VI MOSSES {MUSCI): SP HAGNACE/E—ANDRE.KACE^?: 171 



find their nearest analogies in these forms. The central mass 

 of cells, both in position and origin, corresponds to the 

 columella in these genera, and the archesporium arises by the 

 division of the amphithecium into two layers by tangential 

 walls, and the inner of these two layers, in contact with the 

 columella, becomes at once the archesporium. By rapid cell 

 division the upper part of the sporogonium becomes globular, 

 and is joined to the foot by 

 a narrow neck, much as in 

 Notothylas (Fig. 8 i ). The 

 single - layered wall of the 

 young sporogonium becomes 

 six or seven cells thick, and 

 the columella very massive. 

 The one -layered archespor- 

 ium also divides twice by 

 tangential walls, and thus is 

 four-laj'ered at the time the 

 spore mother cells separate. 

 All the cells of the arche- 

 sporium produce spores of 

 the ordinary tetrahedral form. 

 The so-called " microspores " 

 have been shown conclu- 

 sively to be the spores of a 

 parasitic fungus.^ The layer 

 of cells in immediate contact 

 with the archesporium on 

 both inner and outer sides 

 has more chlorophyll than 

 the neighbouring cells, and 

 forms the " spore-sac." 



The ripe capsule opens 

 by a circular lid which is indicated long before it is mature. 

 The epidermal cells where the opening is to occur grow less 

 actively than their neighbours, and thus a groove is formed 

 which is the first indication of the operculum. The cells at 

 the bottom of the groove have thinner walls than the 

 other cells of the capsule wall, and when it ripens these 

 dry up and are very readily broken, so that the operculum 



^ Nawaschin (i). 



Fig. 81. — Median longitudinal section of a nearly 

 ripe sporogonium of ^. acuti/oliuiii, X 24 ; /•$, 

 pseudopodium ; sfi, spores : col. columella (after 

 Waldner). 



