12 HANDBOOK OF BRITISH MOSSES. 



ticulated, branched, and very irregular in outline, though with 

 rare exceptions smooth and even. They are often hyaline at 

 the tips, but below of a more or less decided brown, inclining 

 sometimes to purple, red, tawny, etc., and, as the plant ad- 

 vances in growth, multiply exceedingly (Plate 4, fig. 6). They 

 penetrate more or less deeply into the soil, or crumbling and 

 decayed surface of rocks or bark, and sometimes on calcareous 

 rocks absorb the portion immediately beneath them, so that 

 each part, like the shields of Lecidea immersa, is sunk in a 

 little cavity. They are, however, by no means confined to the 

 base of the stem, but frequently, though by no means uni- 

 versally, they clothe almost the whole surface more or less 

 densely, between the intervals of the leaves, often forming, as in 

 Aulacomnion palustre (Plate 18, fig. 5), a thick woolly mass. 

 In some cases they are produced also from the base of their 

 leaves, or even from their disk. Conferva castanea and Con- 

 ferva muscicola, of English Botany, are undoubtedly develop- 

 ments of this nature. But not only do these roots occa- 

 sionally give rise to a mass resembling the true primary 

 threads as mentioned above, but amongst certain Hypna they 

 produce a little bud, quite different from the parent plant, 

 which gives rise to the sexual organs which were necessary 

 for the reproduction of the species constituting what is called 

 the quasi- monoicous inflorescence. In Atrichum undulatum 

 (Plate 19, fig. 4) they form a sort of rope, which frequently 

 generates buds. 



The adventitious rootlets not only seem to fix the plant 

 firmly, but they often act as a protection from severe cold, 

 and in many cases either absorb nutriment directly from the 

 matrix like the primary roots, or they imbibe and retain for a 

 time the moisture which is necessary for the support of the 

 plants. In some cases, where the branches are closely packed, 



