THE VASCULAR CRYPTOGAMS 95 



stem on the upper side of the bud, so as completely to 

 shut it in. Our figure shows the bud just before it is 

 quite enclosed, while there is still a crevice left above 

 it, between the stem and the leaf-sheath. When this 

 passage is once shut, it never opens again ; the bud goes 

 on developing within a closed chamber. It lives to 

 some extent at the expense of the surrounding tissue, 

 and eventually breaks through the base of the leaf -sheath, 

 and at last reaches the light of day. Seen from outside, 

 these branches appear to arise below the node, which of 

 course is not the case really. Endogenous buds are very 

 rare, and we see that those of Equisetum are not among 

 them, but only become enclosed after they have started 

 in the usual way, as superficial outgrowths. 



Another peculiarity in Equisetum is the arrangement of 

 the adventitious roots, which do not grow on the main 

 stems, but are always in connection with lateral buds. 

 As a rule, one root (occasionally more) is formed at the 

 base of each branch, arising on its lower side, just below 

 its first leaf-sheath. On the aerial branches these roots 

 generally remain undeveloped, while the branch goes on 

 growing. On the rhizome the reverse is the case, for, as 

 a rule, the buds themselves are abortive, while the roots 

 which they bear grow vigorously. The root grows at the 

 apex by means of a single apical cell of the same pyra- 

 midal shape as that of the stem, from which it differs, 

 however, in forming walls parallel to the free base, in 

 addition to those parallel to the sides. The cells thus cut 

 off at the end increase and multiply very rapidly, and 

 form the root-cap. All the rest of the root is formed from 

 the segments cut off from the three sides of the apical 

 cell. The mode of growth is much the same as in the 

 Fern-root, shown in Fig. 27 (p. 54). 



