BRYOPHYTA. 



701 



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. 



AndreceacecB. — 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 



Kg. 398.— Mosses. 



1 A germiDatin:; spore. 2 a Moss-protoneraa. 3 Protonema giving rise to a bud from which will arise a leafy moss-shoot. 

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

 6 Tip of a female shoot with archegonia; two of them containing sporogouiums 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. 1,2^3x350-400; *xl5; 6x80; ^ x 6. 



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

 (cf. fig. 397 13). 



BryaceoB. — 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 Mo.ss {Schistostega osniundacea) have been already 

 described (cf. vol. i. p. 385, and PI. I. fig. p). The leafy shoots become rooted by the 

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

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



