328 



PART III. THE CLASSIFICATION OF PLANTS. 



B 



forms (Sphagnaceas, Andreseaceee) it grows out into a long leafless 

 stalk, the pseudopodium, which carries up the fertilised arche- 

 gonium. on its apex. The venter of the archegonium also grows, 

 forming, either by itself or together with the adjacent tissue of 

 the shoot (as commonly in the Hepaticae) , an investment, termed 

 the calyptra, which surrounds the developing embryo within and, 



for a longer or shorter time, keeps 

 pace with its growth. 



The gametophyte, though it can- 

 not produce gonidia, has a re- 

 markable power, especially in the 

 Mnsci,of reproducing itself vegeta- 

 tively. This is effected frequently 

 by the gemmce, formed from va- 

 rious parts of the body : the 

 leaves, for instance, in the foliose 

 Hepaticas ; or in distinct recep- 

 tacles termed cupules, as in the 

 Marchantieae and some Musci. 

 The gemmae are either unicellular 

 or multicellular, and, in the latter 

 case, may be either spherical or 

 flattened in form. In the branched 

 forms vegetative propagation is 

 effected by the dying away of 

 the main shoot or of the larger 

 branches, the smaller branches 

 becoming isolated and constitut- 

 ing independent plants. In the 

 Musci almost any part is capable, 

 under favourable conditions, of 

 growing out into protonemal fila- 

 ments on which new adult shoots 

 are developed. 



With regard to the histology of 

 the adult shoot, it need only be 

 pointed out that rudimentary vas- 

 cular tissue, absent in the Ilepa- 

 ticae, is to be found in the stems 

 and the midribs of the leaves of many Musci; and, further, that the 

 epidermis is not clearly differentiated as a tissue-system, and is 



FIG. 236. Funaria hygrometrica. A 

 Longitudinal section of the summit of a 

 weakfemale plant ( x 100) : a archegonia ; 

 b leaves. B An archegonium ( x 550) : 

 b ventral portion with the oosphere ; 7i 

 neck ; m mouth still closed ; the cells of 

 the axile row are beginning to be con- 

 verted into mucilage. C The part near 

 the mouth of the neck of a fertilised 

 archegonium with dark red cell-walls. 

 (After Sachs.) 



