14 STRUCTURAL BOTANY 



d. Growing Points and Mode of Branching 

 a. The Stem 



The growing-point of the stem in Selaginella differs 

 from that in Flowering Plants in the fact that the 

 meristem at the apex shows no trace of differentiation 

 into distinct layers giving rise to definite tissues. In 

 many species, among which is 8. Kraussiana, we find 

 at the apex a single cell, larger than its neighbours, 

 from the divisions of which all the new tissues and 

 organs are ultimately produced. The presence of this 

 single apical cell, as it is called, is very general, though 

 not universal, among Cryptogams, and contrasts sharply 

 with the small-celled meristem characteristic of the 

 Flowering Plants. We shall, however, have better 

 opportunities of studying growth by an apical cell when 

 we come to other groups of Cryptogams, so we will defer 

 the further consideration of this subject. 



The branches arise laterally by the growth of a group 

 of cells just below the apex ; the main axis and its 

 lateral branch, however, often develop so equally that 

 the stem appears to be forked. The branching of 

 Selaginella may be described as an apparent bifurcation 

 or dichotomy. True dichotomy only exists when the 

 growing-point itself is equally divided. The branches 

 of Selaginella, unlike those of Flowering Plants, are not 

 axillary. 



The development of the leaves proceeds in the same 

 way as in the Phanerogams (see Part I. pp. 84, 169, 259). 



ft. Rhizophores and Eoots 



In those species which have special rhizophores, the 

 latter may either grow by means of an apical cell, or 



