374 



MUSCINEM. 



in this group acts like an apical cell, giving rise by a series of longitudinal divisions 

 to several tiers of cells, each tier consisting of three external cells and an internal 

 canal-cell and in other respects resembling the single tier of neck-cells formed in 

 the Liverworts. In this way a long and subsequently twisted neck is formed, 

 consisting of six external rows of cells investing the central row of canal-cells. 

 Below, the cells forming the neck become continuous with the wall of the ventral 

 portion of the archegonium, which consists usually of two (four in Sphagnuni) layers 



of cells. The central cell, which makes 

 its appearance here earlier than in the 

 Liverworts, becomes divided by a trans- 

 verse wall into an upper cell, the ventral 

 canal-cell, and a lower cell, the proto- 

 plasm of which contracts and forms the 

 oosphere (Fig. 256, E). The conversion 

 into mucilage of the canal-cells and the 

 opening of the neck take place in the 

 same manner as in the Liverworts. 



The Sporogomm?!, which results from 

 the fertilised oosphere, attains, in Sphag- 

 num, almost perfect development within 

 the actively growing ventral portion of the 

 archegonium, which becomes transformed 

 into the calyptra; but in all other Mosses 

 the calyptra is torn away from the vagi- 

 nula at its base, by the elongation of the 

 sporogonium, usually long before the de- 

 velopment of the spore-capsule, and (ex- 

 cept in Archidiwn and its allies) is raised 

 up as a cap. The neck of the arche- 

 gonium, the walls of which assume a deep 

 red-brov.'n colour, still for some time 

 crowns the apex of the calyptra. The 

 sporogonium of all Mosses consists of a 

 stalk (the Seta), and the spore-capsule 

 {Theca or Urn); but the former is very 

 short in Sphagnum, Andrecea, and Archi- 

 dium, longer in most other genera, and with its base planted in the tissue of 

 the stem, which, after fertilisation, grows luxuriantly beneath and around the 

 archegonium, forming a sheathlike investment, the Vaginula. The unfertilised 

 archegonia may frequently be seen on the exterior slope of the vaginula, since 

 only one archegonium is usually fertilised in the same receptacle, or it is only 

 in the one first fertilised that an embryo is developed. The capsule has in 

 all Mosses a wall consisting of several layers of cells and a distinct epidermis which 

 sometimes possesses stomata*; the whole of the inner tissue is never used up in 



^ The stomata upon the capsules of Mosses are peculiar, as Schimper has shown, in that the 

 mother-cell of a stoma is not divided into two guard- cells, for the dividing wall does not extend 



Fig. 257. — Fwtaria hygronietrica ; A origin of the sporo- 

 gonium ff in the ventral portion b b oi the archegonium 

 (longitudinal section x 500) ; B, C different further stages of 

 development of the sporogoniumyand of the calyptra c; /t neck 

 of the archegonium (x about 40). 



