22% 
MORPHOLOGY OF MEMBERS. 
therefore never consisted of distinct leaves, but is tlie common basal piece which is 
developed from the floral axis as a whole, and which shows at its margin the original still 
separate leaves as teeth of the bell. The reverse is the case in the leaf-sheaths of 
Equisetum, where an annular wall originally projects round the axis, from which the 
separate leaf-teeth afterwards grow out. In this case also the sheath cannot be con- 
sidered as formed by the cohesion of previously distinct pieces, but the separate teeth 
of the sheath must rather be considered as branches of a single annular rudimentary leaf. 
A similar explanation applies to the bundles of stamens which are generally termed 
coherent (monadelphous, polyadelphous, &c.) stamens. As many protuberances are 
formed originally as there are bundles of filaments to be produced ; and these pro- 
tuberances must be considered as the original staminal leaves which subsequently 
produce by branching a larger or smaller number of stalked anthers (as e.g. in Hypericum, 
Callithamnus, &c.). Cohesions of parts originally distinct are rare ; examples are fur- 
nished by the connate inferior ovaries of two opposite flowers of an inflorescence in 
Lonicera alpigena, the fruits of Benthamia fragifera which cohere into a large pseudo- 
berry, and the cohesion of the two stigmata in the flower of Asclepias to each other and 
to the anthers. The anthers of Gompositse are not truly coherent, but only glued 
together by their sides. 
Much more common than actual cohesion is the abortion of members already 
formed. Thus, for instance, the paripinnate leaves of some Leguminosae^ originate as 
imparipinnate leaves ; the terminal leaflet which is finally aborted is at first in the bud 
even larger than the lateral leaflets ; but, as development progresses, it is so retarded 
that in the mature leaf it overtops the origin of the uppermost lateral leaflets only as a 
minute point. In the same manner the v^hole (branched) leaf-blades of many Acacias 
are also abortive, and are replaced by the petiole (phyllode), which is then expanded 
in its median plane. Still more complete is the abortion of the leaves from the axils of 
which spring the branches of the panicles of Grasses ; and in this class whole flowers 
are often aborted. In diclinous Phanerogams the unisexuality of the flowers 
usually depends on the abortion of the stamens in the female, of the carpels in the 
male flowers. Sometimes only one of several stamens is aborted, as in Gesneraceae 
{e. g. Columnea, where it is transformed into a small nectary) ; and the same occurs 
with the carpellary leaves [e.g. in Terebinthaceae). In all these cases the structure which 
is afterwards abortive is actually present in the bud or even later, but its further 
growth ceases. The comparison, however, of nearly related plants shows that very 
commonly certain members are wanting in the flower the presence of which might 
be expected from the position and number of the others and from their presence 
in nearly related forms, although in such cases even the earliest condition of the 
bud does not exhibit a trace of the absent member. Since from the point of view 
of the Theory of Descent it must be assumed that nearly related plants are descended 
from a common ancestral form, the absent member may in such cases also be sup- 
posed to be aborted, only the arrest of development which has once taken place at an 
early period is so complete and has become so hereditary, that even its first rudiment 
is suppressed. The true theory of the structure of many flowers, and the reference 
of different forms of flowers to common types, often depends on the restoration of 
aborted members of this kind; but to this we shall recur in detail in Book II, when 
treating of Phanerogams. 
Sect. 29. Reproduction; Sexual Organs; Alternation of Generations. 
Reproduction, or the production of new individuals, is generally brought about 
by particular portions of an individual becoming detached, which then have the 
power, first of all of producing new organs of nutrition, and afterwards of continuing 
^ Hofmeister, Allgemeine Morphologie, p. 546. 
