3° 



LECTURE III. 



and other ]Monocot3-ledons, or close beneath the growing point of the stem, so 

 that this is finally covered by a dense feltwork of roots, like the stems of many 

 tree-ferns. If the foliage shoot of the moss under consideration is dorsiventral, and 

 expanded in an oblique or horizontal position, with the upper and under side differently 

 organised, root-fibres arise only in acropetal succession from the shaded side turned 

 towards the substratum. In all these points, the rhizoids of the moss completely 

 resemble the typical roots of vascular plants ; the abnormality consists only in that, 

 in keeping with the simple cellular structure of the moss, they consist not of 



Fig 20. — A, ß, C germination of Fititaria hygro>n€ty 

 the soil. From the creeping protonema, which branches at 

 the soil. (After Müller ; highly magnified.) 



' (a Moss) ; D older seedling creeping on the surface (a. />) of 

 and forms leafy shoots at /v/, arise roots which penetrate into 



masses of tissue, but of jointed cell filaments. However, so far as this anatomical 

 structure admits, the relations of growth agree also with those of true roots : 

 a long cell occupying the end of the root-fibre of the moss corresponds to the 

 growing and cell-forming end of a phanerogamous root, and the growth in 

 length takes place only in this one cell ; its free end corresponds to the growing 

 point, and further backwards it represents the portion of a root which is becoming 

 elongated. New segments are added to the root-fibre by obliqueh' placed walls, and 



