264 



THIRD GROUP.— VASCULAR CRYPTOGAMS. 



The position of tlie lateral buds is peculiar, and gave occasion to the view that 

 the branching of the Equisetaceae is endogenous from interior cells of the stem. 

 The branches are placed vertically beneath the angle between every two leaf-teeth, 

 and therefore alternate with them. The young branches originate in a single super- 

 ficial cell of the growing point of the stem, which is always opposite a depression, 

 never opposite a ridge, in the foliar sheath. The firs-t three divisions of the mother-cell, 

 was observed by Sachs and confirmed by Janczewski, are inclined in three directions 

 in such a manner, that an apical cell with the form of a three-sided pyramid is at 



once produced, and the first three divisions 

 are therefore the first three segments of 

 the cell. But soon the young bud is sur- 

 rounded by the luxuriantly growing tissue 

 of the sheath, and as this unites with the 

 surface of the stem above the bud, the latter 

 is completely enclosed by tissue and has the 

 appearance of being endogenous in origin 

 (Fig. 218). Lateral buds from the rhizome 

 of E. Telmateja and E. arvense in late 

 autumn and early spring will usually show- 

 in longitudinal section all stages in the 

 development of the buds. After they have 

 formed several foliar cushions and their 

 apex is covered by a compact envelope 

 of leaves, they break through the base of 

 the sheath ; they may remain dormant for 

 some time, as is shown by the fact that 

 buds burst into activity when underground 

 nodes of ascending stems are exposed 

 to the light. It may be assumed that as 

 many buds as leaf-teeth are originally 

 formed, and on the erect leafy stems of 

 E. Telmateja, E. arvense and others they 



V^r. . # all develope, and produce the many slender 

 ,_^ I green foliage-shoots found in these species. 



In other species the branching is more 

 scanty ; some like E. hiemale usually have 

 no aerial lateral shoots, except when the 

 terminal bud of the stem is injured, 

 in which case the next node below puts out a shoot. Branches do not usually 

 appear on rhizomes in complete whorls, but only two or three together ; but 

 these are more vigorous and develope either new rhizomes or ascending stems. 

 Since in the cases first described the buds are produced like the leaves in strict 

 acropetal succession, we may assume that, where the shoots develope only at a late 

 period and under the influence of accidental circumstances, the buds have up to that 

 time remained dormant in the interior. 



The roots are formed in whorls, one immediately beneath each bud, but they 



Fig. 219. Longitudinal section through an underground 

 bud of Eqiiisetum arvense ; ss apical cell of the stem, b to £b 

 the leaves, k, Ji> two buds ; the transverse lines in the stem 

 show the position of the diaphragms. 



