338 



MESSES. CYEIL WEST AIS^D H, TAKEDA ON 



Earmer (14) follows Hegelmaier in ascribing to tlic flat apex of the stem a layer of 

 columnar cells in wMch most of the divisions are anticlinal, periclinal divisions occurring 

 at rare intervals. The infrequent occurrence of periclinal divisions was correlated with 

 the slow growth in length of the stem in this genus. 



A similar conclusion was arrived at by Wilson Smith (30, p. 228), who adds, however, 

 that in longitudinal sections of small plants the stem apex is distinguishable as a slight 



elevation . 

 Scott ai 



d HUl 



on 



the 



other hand, bring forward, with 



some 



vation 

 In ou: 



evidence in favour of Hofmeister's original conception of a single apical cell, 

 opinion no importance should be attached to the presence of a single cell of slightly 



larger dimensions than its 



3 



hbours, since several large cells 



can 



,11 y be found 



gularly distributed over the entire surface of the apical region of the stem. 



More 



cells often possess a comparatively large nucleus, and may possibly represent 



leaf-primordia. 



Text-fig. 3. 



L E^F 



Isoetes lacvstris : longitudinal section through the apex of the stem. The plane of the section corresponds 



to that of the main furrows. G. P. = growing-point of the stem, x 300. 



A careful examination of many series of microtomed sections, both transverse and 

 longitudinal, which were compared with thick hand-sections cleared with potash or 

 ' eau de Javelle,' has revealed the true apex of the stem as a relatively large conical 

 protuberance at the base of the funnel-shaped depression in the centre of the leaf -rosette 

 ( t€^xt-figs. 1, 2, 3 ; PL 39. figs. 65-72). 



We have observed this conical mass of tissue at the apex of the stem of four distinct 



m 



species, namely, I. Japonica, I. lacustris, I. Systrix, and I. velata * ; it occurs even m 

 the very youngest specimens of I. japonica and of I. laciisftis which we examined. 

 This protuberance has probably been mistaken for one of the leaf-rudiments to which, 



« 



We 



