464 
VASCULAR CRYPTOGAMS. 
and annoHnum and of the creeping shoots of Z. inundatum; yet it arises in such 
a manner that the branching ma}^ be regarded as being closely allied to dichotomy. 
The bifurcation of the fertile branch of L. alpinum presents another form of 
dichotomy (false dichotomy), for here the growing-point is extended by the develop- 
ment of two new growing points, one on the right and the other on the left side of 
it; the central one then ceases its activity, whereas that of the two lateral ones 
commences, so that the apex of the parent shoot becomes indistinguishable. Those 
Lycopodiese which have their leaves arranged in four rows, and which resemble the 
Selaginellese (Z. complanalum, chamcEcypartssus), branch in one plane only, which 
coincides with that of the larger leaves ; whereas those species which have their 
leaves arranged spirally or in whorls, branch in various intersecting planes. Hegel- 
maier recognised the bulbils which occur in several species (Z. Selago, lucidum, 
reflexum) as being peculiarly modified branches. They arise on the shoot in the 
place of leaves. They fall off of themselves, and are provided with a few leaves and 
a rudimentary root. 
Since the leaves are closely placed by the side of and above each other from the 
first, so as to cover the whole surface of the stem, there are no internodes (as also in 
Ophioglossum, Marattia, Asptdium, Isoe/es) ; and not only so, but the outer cortical 
layer of the stem is genetically connected with the tissue of the bases of the leaves. 
The leaves become separated the one from the other by subsequent intercalary 
growth, and in many cases the base of the leaf becomes sharply defined from the 
stem. 
The first rudiments of the leaves of Lycopodiese appear as multicellular lateral 
protuberances of considerable breadth upon the growing apex of the stem. They 
grow at first apically, but this soon terminates in the formation of a hair-like 
prolongation ; all further growth is intercalary at the base of the leaf. The size and 
form of the leaves are very diff'erent in the various species, but they are always 
simple unbranched, and not stalked but sessile with a narrow base. Occasionally 
their surfaces, with the exception of the free apices, are closely applied to the stem 
(as is the case in Thuja), but more commonly the leaves are quite free. They are 
acicular, or at any rate of small width, and, as in all Dichotomese, a mid-rib only and 
no lateral veins is present. 
The phyllotaxis is sometimes verticillate, sometimes spiral, and both kinds may 
occur on the same plant. The whorls may consist of pairs of leaves which 
decussate, or of three, four, or more, and are arranged in creeping stems on zones 
the planes of which are oblique to the long axis of the stem. The number of leaves 
in a whorl varies even on the same shoot. According to Hegelmaier, the whorls are 
true ones ; the leaves composing them are developed simultaneously and at the same 
level at the punciuni vegetaimiis. Where the phyllotaxis is spiral it is so from the 
first, and the divergence undergoes no important modification. The small and very 
various divergences of the leaves are remarkable, as Braun pointed out ; he found in 
Z. clavatum the following divergences, f , \, -fj, as well as whorls consisting 
of from four to eight leaves ; in Z. annoiinum they were f , f , and whorls of four or 
five leaves; in Z. inundatum f and whorls of five leaves (Bot. Zeit. 1872, p. 815). 
The much bifurcated, multiangular, thin stem of Psilotum grows by means of 
a three-sided apical cell, which, according to Nageli and Leitgeb, forms (in the 
