GROUP II. BRYOPHYTA. 



313 



by itself or together with the adjacent tissue of the shoot (as 

 commonly in the Hepaticse), 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 has a remarkable power, especially in the 

 Musci, of reproducing itself vegetatively. This is effected fre- 

 quently by the gemmce, formed from various parts of the body : 

 the leaves, for instance, in the foliose Hepaticse ; or in distinct 

 receptacles termed cupules, as in 

 the Marchantiese and some Musci. n 



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 be- 

 coming isolated and constituting 

 independent plants. In the Musci 

 almost any part is capable, under 

 favourable conditions, of growing 

 out into protonemal filaments on 

 which new adult shoots are de- 

 veloped. 



With regard to the histology of 

 the adult shoot, it need only be 

 pointed out that rudimentary vas- 

 cular tissue, absent in the Hepa- 

 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 differ- 

 entiated as a tissue- system, and is 

 destitute of stomata. It is true 

 that in some Hepaticse (e.g. Antho- 

 ceros, Marchantia, etc., Fig. 199) 

 there are structures in the super- 

 ficial layer which are erroneously 

 called stomata ; these are merely 

 pores, and differ altogether in 



FIG. 195. Futiaria hygrometriea. A 

 Longitudinal section of the summit of a 

 weak female plant (x 100) raarchegonia ; 

 b leaves. B An archegoninm ( x 550) : 

 b ventral portion with the oosphere ; 

 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.) 



