Metaphyla Selaginella. 135 



in amount. The fibro-vascular strand of the leaf is an offset 

 from that of the stem. 



Root. The roots do not require detailed mention, being 

 fundamentally the same in structure as the stem, though 

 the arrangement of the tissues of the fibro-vascular strand 

 is somewhat different. Numerous root-hairs are given off 

 from the rootlets as they enter the soil. Structures known 

 as rhizophores are developed, as already mentioned, from 

 certain parts of the stem, near the bases of branches. 

 These find their way to the ground and there give origin to 

 true roots. The rhizophores have no root-caps, but are not 

 therefore necessarily branches ; for we have in botanical 

 morphology numerous instances of true roots which have, 

 while still aerial, no root-cap, afterwards obtaining one when 

 they touch the soil. 



It was stated in the last section FIG. 60. Selaginella. APEX 



. OF THE STEM. 



that the apex of the stem in the lower 



plants consisted usually of a single 



cell, known as the apical cell, whilst 



the terminal growing points of the 



higher plants usually consisted of a 



group of cells known as primary 



meristem. In Selaginella and its 



allies we have numerous transitional 



stages between the single apical cell and the multicellular 



state. We will take an instance where the unicellular state 



is retained. Even in the very terminal portion of the stem, 



and not far from the apex itself, we find the young leaves 



mapped out in primary parenchyma. The meristem is 



formed by successive segmentations from either side of the 



apical cell, each segment producing by subdivision a group 



of cells forming the rudiment of a leaf. 



Asexual reproductive organs. The sporangia are not 

 developed on all leaves of the sporophyte, but on certain 

 leaves towards the ends of certain branches. The fertile 

 branches have their terminal leaves modified (a) in form, 



