198 MORPHOLOGY. 



VIII. THE HORSETAILS (EQUISETACE.E). 



1 10. The spore-cell of the Equisetacea expands into an utricle, at 

 one extremity of which new cells are formed, that gradually acquire 

 the form of a many-lobed flat expansion, a simple cellular layer, 

 several cells of which become elongated into filiform adhering fibres 

 (the proeinbryo). At one point of this proembryo there appears 

 a cellular node, which develops itself upwards into the bud, stem, 

 and leaf, and downward to a root. The main stem appears, how- 

 ever, to die off very speedily in the case of most, while in its place 

 are developed from the axillary buds of the first leaves lateral 

 branches, which run horizontally below the surface, never assume 

 a green colour, and whose lateral branches partly rise in a vertical 

 direction, and appear above the ground. All the stems of the 

 EquisetacecR are round, mostly furrowed and regularly elongated 

 between the successively ranged leaves (internodium, internode). 

 At the roots of the leaves the stems are somewhat contracted, and 

 easily break off (nodi, nodes). The leaves are small, scaly, ranged 

 in a whorl, and grown together by the lower part of their margin 

 into a sheath closely surrounding the stem. The axillary buds of 

 the stem above ground burst in a remarkable manner through the 

 base of the leaves, and form whorls ; these have also, less frequently, 

 lateral branches. The individual lateral branches are not invariably 

 elongated, but enlarge spherically between every two circles of 

 leaves, become fleshy, and then readily separate from the stem into 

 their individual joints. 



I have not myself enjoyed any opportunity of observing the germina- 

 tion of the EquisetacecE ; and the description given is taken from 

 Vaucher* and Bischoff.f But both leave very much to be desired. It 

 is inconceivable to me how any one can say " new cells appear, new 

 cells seem to occur between," without even touching upon the obvious 

 inquiry " whence come these cells ? " It is an evidence of the difficulty 

 that there is in giving a correct account of what we have observed ; and 

 assertions of this nature are all but untrue, since it merely amounts to 

 this, that in one case he saw a few, and in others many cells, the position 

 and interposition of the cells originating in fancy and not from observa- 

 tion. We must remark, that in the primary stem the first leaf-circles 

 are scarcely removed from each other, and that the expansion of the 

 internodes of the stem begins higher up. 



111. At the points of the stems above ground, or of their 

 branches (often in peculiar branchless stems), several closely con- 

 tiguous leaf-whorls become developed into an ovate fructification. 

 The individual leaves (sporopliylld] change in a peculiar manner, 

 assuming the form of a hexagonal disc, attached by a pedicle at its 



* Mem. de Mus. d'Hist. Nat. vol. x. p 429. 

 f Die kryptogamischen Gewachse, p. 40, et seq. 



