STOMATA AND CONCEPTACLES OF MAKCHANTIA. 345 



FiO. 128. 



At the period of fructification, these fronds send up stalks, which 

 carry at their summit either round shield-like disks, or radiating 

 bodies that bear some resemblance to a wheel without its tire 

 (Fig. 128) ; the former carry the male organs or antheridia, and 

 the latter, at an early period, the female organs or archegonia, 

 which afterwards give place to the sporangia or spore-cases.' But 

 besides these, the frond usually bears upon its surface (as shown 

 in Fig. 128) a number of little 

 open basket-shaped " concep- 

 tacles," whose nature and pur- 

 pose will be presently explained. 

 The green surface of the frond 

 of this Liverwort is seen under 

 a low magnifying power to be 

 divided into minute diamond- 

 shaped spaces (Fig. 129, a, a, a) 

 bounded by raised bands (e, e) ; 

 every one of these spaces has in 

 its centre a curious brownish- 

 colored body (6, h), with an open- 

 ing in its middle, which allows 

 a few small green cells to be seen 

 through it. When a thin vertical 



section is made of the frond (b), it is seen that each of the 

 lozenge-shaped divisions of its surface corresponds with an air- 

 chamber in its interior ; which is bounded below by a floor (a, a) 

 of closely set cells (from whose under surface the radical fila- 



Fio. 129. 



Frond o( MarcJutniia polymffrpha, with gera- 

 miparous conceplacles, and lobud receptacles 

 bearing pistillidia. 



Aj Portion of frond of MarcliaTitia poli/vwrplui seen from above; a, a, lozenge-sliaped divisions; 

 6,6, stomata seen in the centre of the lozenges; c, c, greenish bands separating the lozenges: — B, 

 vertical section of the frond, showing a, a, the dense layer of cellular tissue forming the floor of the 

 cavity d.d; 6, 6, cuticular layer, forming its root ; c, c, its walls ; /, /, loose cells in its interior ; g, 

 stoma divided perpendicularly; 7i, rings of cells forming its wall; z, cells forming the obturator 

 ring. 



ments arise), at the sides by walls (c, c) of similar solid paren- 

 chyma, the projection of whose summits forms the raised bands 

 on the surface, and above by a cuticle (i, b) formed of a singlfe 

 layer of cells ; whilst its interior is occupied by a very, loosely 



' In some species, the same shields bear both sets of organs ; and in Marchantia 

 androgyna, we find the upper surface of one half of the pelta developing antheridia, 

 whilst the under surface of the tinder half bears archegonia. 



