128 



STRUCTURAL BOTANY 



The leaves are arranged in a spiral, with a divergence 

 of |, that is to say each leaf is separated from the one 

 next above it by three-eighths of 

 the circumference of the stem, so 

 that in following the spiral three 

 times round the stem we pass 

 eight leaves, and find that the 

 ninth lies vertically above that 

 from which we started (see Part 

 I. p. 14). The leaves themselves 

 are inserted on the stem with a 

 fairly broad base ; they are ovate 

 in form, pointed at the tip, and 

 traversed by a distinct midrib, 

 though not otherwise veined (see 

 Fig. 58). The rhizoids are white 

 when quite young, but soon be- 

 come brown. The above descrip- 

 tion applies especially to the barren 

 stems ; we shall refer more parti- 

 cularly later on to those which 

 bear the reproductive organs. 



FIG. 58. Funaria hygro- 

 metrica ; general view of 

 a fruiting specimen, g, 

 the leafy Moss plant or 

 oophyte ; sp, the fruit or 

 sporophyte generation, 

 consisting of the seta, s, 

 and the theca, th ; c, the 

 calyptra. Slightly mag- 

 nified. (After Sachs.) 



1. THE LEAFY STEM 

 a. Structure 



The anatomy of the Moss plant, as represented by 

 Funaria, is simple, but yet shows a fairly well-marked 

 differentiation of tissues. In the mature stem three 

 distinct zones can be distinguished, epidermis, cortex, 

 and central cylinder. The epidermis is one cell thick in 

 most places, though here and there a double row of cells 



