MARCHANTIA. 



[ 490 ] 



MARCHANTIA. 



convex above ; and on the under surface of 

 the base of each lobe are found delicate 

 membranous processes with toothed mar- 

 gins. The membranes of each two adjoin- 

 ing lobes form a perichcetium (fig. 448) 

 alternating with the lobes, concealing be- 

 tween them the archeyonia, which are at- 

 tached by their bases, and have their mouths 

 pointing' downwards. The archegones of 



Fig. 448*. 



Marchantia polymorpha. 



Archegonia in various stages. 



Magnified 100 diameters. 



Marchantia are flask-shaped sacs with a 

 long slender neck (fig. 448*), containing 

 in their cavity a cell (germ-cell), which 

 after fertilization becomes developed into an 

 oval cellular body, the young sporangium. 

 In the course of the development of this, it 

 soon fills the cavity of the archegone, which 

 then begins to grow with it, and subse- 

 quently forms a loose sac around it the 

 epiyonium finally ruptured at the point, so 

 as to exhibit four or five teeth or valves, 

 which become recurved (fig. 449). Mean- 

 Fig. 449. 



Marchantia polymorpha. 



Vertical section of Fig. 448, showing sporanges in situ, 



bursting to discharge the spores and elaters. 



Magnified 10 diameters. 



while another envelope grows up around 

 the epigone, appearing at first as a mere 



ring surrounding it (fig. 448*), but 

 ultimately rising up so as to enclose it, 

 remaining open however at the summit; 

 this is the perigonium. In its young stages 

 the sporange is a mere oval mass of poly- 

 gonal cells ; but a distinction may soon be 

 detected between a cortical or peripheral 

 layer and the internal mass. The cells of 

 the former remain firmly united into a 

 membrane forming the wall of the sporange. 

 These cells grow so as to assume an elongated 

 form, and when mature exhibit internally a 

 spiral-fibrous secondary deposit (PL 40. fig. 

 35), analogous to that of the cells of the 

 anthers of Flowering plants. The cells of 

 the internal mass present at an early period 

 the appearance of a large number of fila- 

 ments radiating from the centre of the 

 sporange to the wall. These soon become 

 free from each other ; and it may then be 

 perceived that some are of very slender 

 diameter, and others three or four times aa 

 thick. The slender ones are developed at 

 once into the long elaters (PI. 40. tig. 36) 

 characteristic of this genus, containing a 

 double spiral fibre, the two fibres, however, 

 coalescing into one at the ends (fig. 37). 

 The thicker filaments become subdivided by 

 cross partitions, and break up into squarish 

 free cells, which are the parent cells of the 

 spores, four of which are produced in each 

 (PI. 47. figs. 10-13). The spores of M. po- 

 lymorpha have but a single coat ; and their 

 contents are bright yellow when mature. 

 When they germinate, the contents are 

 converted into chlorophyll ; and the growth 

 commences by the production of a tubular 

 process from one side of the spore. 



Fig. 450. 



Marchantia polymorpha. 



A collection of grmmae in their involucre. 



Magnified 25 diameters. 



It has been mentioned that M. polymorpha 

 1 does not fruit freely in the shade. Under 



