FiLICINEm. 
433 
The Formation of Adventitious Buds ^ which do not result from the terminal 
branching of the stem, is, in Ferns, connected with the leaves. These buds make 
their appearance on the leaf-stalk or on the lamina itself. The shoots of Pleris 
aquilina which spring from the leaf-stalk (Fig. 301) stand at the back of the 
individual leaf-stalks near the base; in Aspidium Filix-nias (Fig. 302) they arise 
at a moderate height above the insertion, usually on one of the lateral edges of the 
leaf-stalk. In both cases Hofmeister states that they are formed on the young 
leaf-stalk even before the first appearance of its lamina, and before the differentiation 
of its tissue. A single superficial cell of the leaf-stalk is the mother-cell of the new 
shoot; and as the surrounding tissue of the leaf-stalk grows like a wall around them, 
they may, as in Pteris, be placed in a deep depression, where they sometimes remain 
dormant for a long period. Even when the leaf has long died away, the leaf-stalk 
still remains succulent up to the bud, and filled with food-materials; and in 
Aspidium Filix-mas vigorous stems are not unfrequently found with a number of 
leaves at their posterior end still attached to the leaf-stalk of an older stem. In 
some cases, as in Struthiopteris germanica, the buds produced on the leaf-stalks 
develope into long underground stolons furnished with scale-leaves, which become 
erect at the end and unfold a crown of foliage-leaves above ground. In Ncphro- 
lepis undulata they swell at the end into tubers. Adventitious buds spring from the 
lamina, especially in many species of Asplenium ; in A. furcatum, e.g., often in large 
numbers from the middle of the upper surface of the pinnae; in A. decussaium from 
the base of the pinnae (or axillary on the mid-rib.?). Ceratopteris thalictroides not unfre- 
quently produces buds in the axils of all the divisions of the leaves, which, especially 
when the detached leaf is laid upon damp ground, develope rapidly, and grow into 
vigorous plants. According to Hofmeister, these buds also spring from superficial 
cells of the leaf. The long pendulous leaves of some Ferns touch the ground with 
their apices, root, and sometimes also put out new shoots from these points {e.g. 
Chrysodium flagetliferum, Woodivardia radicajis, Sec). 
The Roots. During its growth the stem is usually constantly forming new roots 
in acropetal succession, which, in the creeping species, become at once fixed to the 
substratum. [As a rule they are developed quite endogenously, but in Ceratopteris 
thalictroides, according to Kny, they arise from cells immediately beneath the 
epidermis. According to Conwentz, a distinct relation can usually be observed 
between the number of the roots and that of the leaves.] In Pteris aquilina the 
new roots appear close behind the apex, and, both in this species and in Aspidium 
Filix-mas, they also proceed from the adventitious buds of the leaf-stalk while 
still very young. It has already been mentioned that, in the last-named species, 
when the mature stem is completely covered by leaf-stalks, all the roots spring 
from them and not from the stem. In Tree-ferns especially the lower part of 
the erect stem is entirely covered by slender roots, which grow downwards, forming 
an envelope several inches thick before they penetrate the soil, and thus give a 
both in reference to the formation of leaves and to the terminal branching of the stem. [According 
to Sadebeck, the pinnae are developed as lateral outgrowths, but the branching of the veins is the 
result of the dichotomy of the marginal cells ; see s.nprai\ 
^ [On the development of these adventitious buds, see Heiniicher, Sitzber. d. Wien. Akad. 1878 
and 1881.] 
F f 
