370 



VASCULAR CRYPTOGAMS. 



tlie first rudiments of tlie slieath-teeth appear as protuberances at regularly dis- 

 tributed points, each of them ending in one or two apical cells (Fig. 276) \ 



The Equisetaceae are the only class of plants the Branching of which depends 

 exclusively on the formation of endogenous lateral buds. These are formed in the 

 tissue of the youngest foliar girdle at points alternating with the sheath-teeth 

 long before the differentiation of the fibro-vascular bundles. The position of the 

 spot where they originate has not yet been precisely determined; it is probably a 

 cell of that layer from which the fibro-vascular bundles originate. Hofmeister 



was the first to show that each bud 

 proceeds from a single cell of the 

 inner tissue ; and although I have 

 myself never seen it in a unicellular 

 condition, I have found rudimentary 

 branches composed^ of only two or 

 four cells ; and these showed that even 

 the first three divisions of the mother- 

 cell of the branch are inclined in three 

 directions in such a manner that a 

 triangularly pyramidal apical cell is 

 produced; and the first three divisions 

 thus form the first three segments. 

 Lateral buds of the rhizome of E. Tel- 

 mateia and E. arvense, late in the 

 autumn or early in the spring, usually 

 show in longitudinal section all the 

 stages of development of endogenous 

 buds. After they have formed several 

 foliar girdles and their apex is covered 

 by a firm envelope of leaf-sheaths, 

 they break through the base of the 

 parent leaf-sheaths. They may also 

 remain dormant for a long period, as 

 is shown by the circumstance that 

 buds break out when the underground 

 nodes of ascending stems are exposed 

 to the light. It may be assumed that 

 there is always as large a number of 

 buds in a rudimentary condition as 

 there are sheath-teeth. On the erect leafy stems of E. Telmateia, E. arvense, and 

 other species, they all attain complete development, and produce the numerous 

 slender green leafy shoots of these species ; in other species the development of 

 the branches is more sparing; some, as E. hyemale, usually form no aerial lateral 

 shoots at all except when the terminal bud of the stem is injured, and then the 



FIG. 277. — Longitudinal section through an underground bud 

 of EquisetKin aruense ; ss apical cell of the stem, b-'ib the 

 leaves; K K' two buds; the horizontal lines across the stem 

 indicate the position of the septa (diaphragms). 



' On the original number and subsequent increase of the sheath-teeth, &c,, compare Hofmeister 

 and Rees, /. c. 



