336 



THE MICROSCOPE AND ITS REVELATIONS. 



summits either round shield-like disks, or radiating bodies that bear 

 some resemblance to a wheel without its tire (Fig. 214=). The former 

 carry the male organs, or antJieridia ; while the latter in the first 

 instance bear the female organs, or archegonia, which afterwards give 

 place to the sporangia or spore-cases. * 



332. The green surface of the frond of Marchantia is seen under a 

 low magnifying power to be divided into minute diamond-shaped spaces 

 (Fig. 215, A, a, a) bounded by raised bands (c, c); every one of these 

 spaces has in its centre a curious brownish-colored body (, Z>), with an 



Structure of frond of Marchantia poly- 

 morpha ; A, portion seen from above ; , 

 a, lozenge-shaped divisions; b, 6, stomata 

 in the centre of the lozenges; c, c, green- 

 ish bands separating the lozenges: B, 

 vertical section of the frond, showing a, 

 a, the dense layer of cellular tissue form- Gemmiparous Conceptacles of Mar- 



ing the floor of the air-chamber, d, d ; the chantia polymorpha: A, conceptacle 



epidermic layer, 6, b, forming its roof; c, fully expanded, rising from the sur- 



c, its walls; /, /, loose cells in its interior; f ace of the frond, a, a, and containing 



g, stoma divided perpendicularly; /i, rings gonidial disks already detached; B, 



of cells forming its wall; i, cells forming first appearance of conceptacle on the 



the obturator-ring. surface of the frond, showing the for- 



mation of its fringe by the splitting 

 of the cuticle. 



opening m 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 filaments 

 arise; at the sides by walls (c, c) of similar solid parenchyma, the projec- 

 tion of whose summits forms the raised bands on the surface; and above 

 by an epidermis (&, V) formed of a single layer of cells; whilst its interior 

 is occupied by a loosely arranged parenchyma, composed of branching 



1 In some species, the same shields bear both sets of organs ; and in Marchan- 

 tia androgyna we find the upper surface of one half of the pelta developing 

 antheridia, "whilst the under surface of the other half bears archpgonia. 



