l82 
MORPHOLOGY OF MEMBERS. 
diaceae always arise so near to the apex, and they assume at so early a period the 
character of dichotomies developed in a bifurcate manner, that, until further inves- 
tigation proves the contrary, they m.ust be considered as such. It is scarcely necessary 
to mention in conclusion that when roots branch dichotomously the bifurcations are at 
first covered by the original root-cap, as is shown in Fig. 138. 
(c) Lea'ves. Bifurcations resulting apparently from true dichotomy occur in the leaves 
of some Ferns, e.g. Platycerium alcicorne^ ] and, according to an older statement of 
Hofmeister, it appears that the branching of Fern-leaves generally commences dicho- 
tomously, although mature leaves mostly resemble a monopodium. On a mid-rib 
forming a continuation of the petiole are placed numerous secondary mid-ribs with 
secondary lacinise (pinnae). Since these branches are apparently always alternate and 
not opposite, and the terminal lobes of the leaves are frequently developed as equally 
strong bifurcations, leaves of this kind may be considered, according to Hofmeister's 
hypothesis, as dichotomies developed in a sympodial (and indeed a scorpioid) manner, 
the mid-rib representing the sympodium, and the apparent lateral branchlets the weaker 
branches (as in Fig. 134, C, p. 178) ; a process which is repeated in the segments of the leaf 
itself when the leaf is doubly or many times pinnate. A similar interpretation may per- 
haps be permitted of the simply pinnate leaves of Cycadeae. The repeated branching 
of the stamens in the male flowers of Ricinus appears, according to Payer ^, to proceed 
from dichotomy, and to a certain extent even from polytomy, commencing at an early 
period. The separate stamens appear as roundish protuberances on the floral axis, and 
each of these immediately forms two or more similar protuberances on its surface, and 
on these the same process is again repeated. When mature, the stamens (Fig. 139) 
appear as if divided dichotomously or trichoto'mously upon long stalks, the branches 
being developed somewhat irregularly. 
^ The petiole of Adianhim pedatum divides above into two equally strong branches, each of 
which forms a helicoid cyme of ramifications arising probably by dichotomy ; the weaker branches 
of the helicoid cyme stand upright and their numerous pinnse form a scorpioid cyme produced 
by further dichotomy. This is one of the most beautiful forms of leaves, the history of the 
development of ^N\\\c\\ would be of unusual interest. 
^ Payer, Organogenic de la fleur, pi. 108, confirmed by Warming I.e. 
Fig. 138.— Dichotomy of the root oi Isoetes lacustris (after 
Hofmeister) (x 400); 1 1' the apical cells of the branches; luh 
the old root-cap formed before the bifurcation ; the two 
root-caps of the branches, stiil covered by the former one ; e 
epidermis parenchyma; z/'fibro-vascular bundle of the root. 
Fig. 139. — Part of a male flower of Ricinus communis 
cut through lengthways ; ff the basal portions of the com- 
poundly branched stamens ; a their anthers. 
