LYCOPODIUM. SPOROPHORE. 183 



elements (Plerome or Procambium), while the forma- 

 tive tissue of the cortex external to it is more typically 

 parenchymatous (Periblem) ; it is limited by a not 

 very definite layer of cells which may be recognised as 

 the Dermatogen. 



The conical apex itself consists of a dome-shaped 

 mass of meristem; the layer of dermatogen, which 

 may be recognised at the base of the cone, may be 

 followed up nearly to the apex, but there loses its 

 identity, the extreme apex being occupied, at least in 

 the more bulky examples, by a group of initial cells, 

 which divide by anticlinal walls ; those at the margin 

 of the group divide also periclinally. Compare this on 

 the one hand with the structure of the apex of the 

 stem of Phanerogams, and on the other with that seen 

 in the Ferns. 



Observe further that the development of the 

 leaves begins by the outgrowth and division (both 

 anticlinal and periclinal) of groups of cells, which 

 constitute multicellular protuberances; these have at 

 first an apical growth, which soon ceases, the further 

 growth being basal and intercalary. 



The origin of the branches may further be observed 

 in these preparations ; it will be seen that they arise 

 in this species below the apex of the main axis, and 

 laterally upon it ; the branching is thus monopodial 

 not dichotomous. 



VIII. Cut transverse sections of one of the thick 

 roots: mount as before, and observe that they re- 

 semble the transverse sections of the stem in the 

 arrangement of the tissues, though the whole structure 

 is simpler : there are usually only three plates of 



