56 



MOSSES AND FERNS 



THAP. 



but there is a rapid lateral growth with results in the formation 

 of two valves, which meet in front much like the two parts of 

 a bivalve shall, and this involucre completely encloses the devel- 

 oping sporogonium. 



In the simplest cases, where the archegonia are borne upon 

 a receptacle^ whicli is raised upon a stalk, e.g., Phgiochasma, 

 Clcvca (Fig. 20, A), the receptacle does not represent, accord- 

 ing to Leitgeb ( (7), vi., p. 29), a complete branch, but is only a 

 dorsal outgrowth of the latter, which may grow out beyond' it, 

 or even form several receptacles in succession. Tlie first indi- 

 cation of tlie recep- 



A. 





B. 



tacle is a dorsal prom- 

 inence whicli soon be- 

 comes almost hemi- 

 spherical, and near the 

 _ .— v: hinder margin the first 

 archegonium arises, 

 without, apparently, 

 any special relation to 

 the growing point. 

 On the lateral margins 

 are then formed two 

 other archegonia, not, 

 however, simultane- 

 ously; and finally a 

 fourth may be formed 

 in front : three or four 

 archegonia in all seem 

 to be the ordinary 



Fig. 20.-A. Chvea sp. A, longkudinal section of 'l^^nil^er. TllC Stalk of 



the thallus showing the dorsal origin of the fc- tllC rCCCptaclc is alsO 



male receptacle ($) ; r, the growing point (dia- .1^,-,,^1 nnnpnrHo-p ni 



gram after Lcitgcb) ; B, Reboulia hemisphwrica ^ < 'Ol ^ai appCnCiage OI 



(Radd.), longitudinal section of very young re- tllC tlialluS, aud UOt 1 



ceptacle with the first archegonium (Q) ; x, the i • - .• .• 



apical cell. X300 (after Leitgeb). ^ d 1 r C C t COntinUatlOU 



of it. 

 The next type is that whicli Leitgeb attributes to GriiuaJdia, 

 Reboulia, Fimbriaria, and some others, but it is not tlie tvpe 

 found in Fimbriaria Calif ornica. In this type tlie structure of 



"The sporongotiial receptacle of the Alarchantierc is sometimes known as 

 the Carpocephalnm. 



