XIV 



L YCOPODINE^E 



471 



according to Strasburgcr,^ usually show two initials in longi- 

 tudinal section (Fig. 247, i). From these initials arc cut off 

 lateral segments which, by further periclinal and anticlinal walls, 

 produce the epidermis and cortex, and secondarily the leaves. 

 Periclinal walls also are formed from time to time in the initial 

 cells, by which basal segments arc cut off, which produce the 

 large central plerome cylinder. 



The leaves arise as conical outgrowths near the stem apex, 

 and owe their origin to the three or four outer cell layers of the 

 growing point. The separation of the epidermis does not occur 



f'iG. ■2\-j.~-Lycopodiuin sclago (L.). A, Longitudinal section of the stem apex, X120; f-,/-, young 

 leaves ; /, i, initial cells ; //, plerome ; B, surface view of the stem apex, showing the group of 

 initial cells, x 260 ; C, longitudinal section of the root-tip ; d, dermatogen ; j)b, periblem ; //, 

 plerome ; cal, calyptrogen ; h, h, root-hair initials, X 120 (all the figures after Strasburger). 



until the leaf has formed a conspicuous conical protuberance. 

 The differentiation of the procambium in the young leaf begins 

 early, and the strand joins the central procambial cylinder of 

 the stem, which, however, is quite independent of the leaf- 

 traces. Each young leaf-trace joins an older one at the point 

 of junction with the stem cylinder, and thus the complete stem 

 possesses two systems of vascular bundles, the strictly cauline 

 central cylinder, and the system of common bundles formed by 

 the united leaf-traces. 



The first elements of the vascular bundles to become 



' Strasburger (10), p. 240. 



