MARCHANTIA. 



[ 412 ] 



MARCHANTIA. 



MARCHANTIA, Micheli. A genus of 

 Marchantieae(Hepaticace8e). The most com- 

 mon species, M. polymorpha, may be taken as 

 a type at once of this genus and of the family. 

 It is a little plant, not uncommon between 

 the stones of damp shady courtyards, the 

 borders of springs, &c., extending itself in 

 bright green thin lamellae of irregular lobed 

 outline, attached to the soil by radical hairs 

 arising on the lower surface. The frond 

 presents an upper and lower epidermis with 

 an intermediate parenchyma, and the lobes 

 are traversed by a kind of midrib. The 

 upper surface is marked by raised lines which 

 cross each other very regularly, leaving be- 

 tween them lozenge-shaped spaces (fig. 448), 



Fig. 448. 



Marchantia polymorpha. 



Lobe of a frond. 

 Magnified 10 diameters. 



in the centre of each of which occurs a 

 stomate, leading to an intercellular space in 

 the parenchyma. The stomates of Mar- 

 chantia are circular, and consist of sixteen 

 cells, arranged so as to form four rings, one 

 upon another, each ring being composed of 

 four cells; they may be best explained by 

 comparing them with a chimney composed of 

 four courses of bricks, each consisting of 

 four bricks laid together to enclose a square. 

 The parenchyma is composed of several 

 layers of cells, which contain much chloro- 

 phyll. The inferior epidermis is clothed by 

 radical hairs, which exhibit a remarkable 

 spiral marking, arising from the projection 

 of a spirally deposited secondary layer in the 

 interior of the tube. 



The fronds do not readily produce spo- 

 ranges in shady places, but when exposed to 

 the light these are produced at the ends of 

 the ribs, at the base of the terminal notches 

 of the lobes. The male structures are pro- 

 duced on different plants from the female, but 

 both are borne on peculiar stalked receptacles. 



The first appearance of one of these recep- 

 tacles is as a little green papilla, surrounded 

 by reddish scales, at the end of one of the 

 principal ribs. As it enlarges it pushes its 

 way through the scales, and the rib on which 

 it is borne elongates to form a pedicel, on 

 which it is raised up perpendicularly above 

 the surface of the frond, ultimately acquiring 

 the form of an expanded cap, in the male 

 receptacles with a sinuate margin (fig. 449), 



Fig. 449. 



Marchantia polymorpha. 



Plant with antheridial receptacles. 



Nat. size. 



in the female with the border developed into 

 eight or nine thick cylindrical lobes (fig. 450). 



Fig. 450. 



Marchantia polymorpha. 



Plant with fertile receptacles. 



Nat. size. 



The male receptacle is concave above, 

 with papillae consisting of the mouths of 

 flask-shaped cavities, in each of which is 

 formed an antheridium (fig. 451). These 

 antheridia are oval cellular bodies lodged in 

 the expansion of the cavity, with a long neck 

 projecting forward through the mouth of the 

 flask-shaped excavation. The cells of the 

 interior of the lower part of the antheridia 

 produce spermatozoids (PI. 32. fig. 32). The 



