BRYOPHYTA. 



70] 



elongation of the axis of the female shoot taking place in the region immediately 

 below the group of archegonia. The capsule is thus hoisted up on a long stalk, 

 though this stalk is no part of the sporogonium (c/. fig. 397 ^^). 



The remains of the Bog-mosses form an important constituent of peat. 



Andreceacece. — A small family, including the single genus, Andrecea. They are 

 amongst the first settlers upon new and inhospitable rock-surfaces, and play an 

 important part as soil-formers (cf. vol. i. p, 266). In them the mode of bursting of 

 the spore-capsule is altogether peculiar amongst Mosses. Four longitudinal slits 



/ ^ 



Fig. 398.— Mosses. 



I A germinating spore. 2 a Moss-protonema. s Piotonenia giving rise to a bud from which will arise a leafy moss-shoot. 

 * Longitiuliiial section of the tip of a male slioot of a Moss ; small, club-shaped antheridia are present between the scales. 

 « Tip of a female shoot with archegonia; two of them containing sporogoniums have enlarged, and in the left-hand one 

 of these two the upper part of the archegonium (calyptra) has been torn from the basal portion. » Leafy female 

 shoot bearing a fully developed sporogonium; the calyptra is still in position, i, «, * x 350-400; < x 15; » x SO; • x 5. 



arise in its wall, and the four valves remain attached to one another at the apex 

 {cf. fig. 397 13). 



Bryacece. — This family includes the vast majority of the Mosses. The germinat- 

 ing spore produces a simple, branching, filamentous protonema (figs. 398 ^ and 398 -) 

 on the surface of the ground, certain of its branches developing as colourless 

 rhizoids and penetrating the substratum. From the protonema the ordinary leafy 

 Moss-plant arises as a lateral bud (cf. fig. 398 3). The curious properties of the 

 protonema of the Luminous Moss (Schistostega osmundacea) have been already 

 described (cf. vol. i. p. 385, and fig. 25a, ^j). The leafy shoots become rooted by the 

 development of rhizoids from their lower extremities, and bear their leaves, as a 

 rule, in three rows, though a slight twisting of the stem often disguises this fact. 



