172 
MORPHOLOGY OF MEMBERS. 
transformed into the sporogonium, a structure without leaves, roots, or branches, 
the sole function of which is the production of spores. A new Moss-plant is, 
on the contrary, constituted by the production of a leaf-bearing shoot from 
a branch of the alga-like Protonema, which branches, strikes root (by root- 
hairs), and is independently nourished. The shoot first produced, from which 
are developed the rest, is termed the Primary Shoot ; it is often more strongly 
developed than its lateral shoots, as in most Ferns, Cycadeae, Coniferae, Palms, 
and Amentiferse. The primary shoot produces Lateral Shoots of the first order 
or Secondary Shoots, these again lateral shoots of the second order, and so on. 
Nevertheless it often happens that lateral shoots of any order take root and 
become detached from the primary shoot; 
they then assume all its peculiarities, and 
may equally be considered as primary 
shoots. But it also happens that the 
primary shoot itself is arrested at an 
early period,, while new orders of shoots 
proceed from it which gradually become 
more vigorous, as in many bulbous and 
tuberous plants. Shoots which become 
detached from the mother-plant when but 
slightly developed, continue to grow by 
independent nourishment, and repeat the 
peculiarities of the primary shoot, are 
called GemmcB or Bulbils ; they are often 
adventitious shoots ; but bulbils may also 
be shoots of normal origin, as in many 
species of Allium. 
Fig. \-2-j.—Aspleiiuon decussatum ; middle part of a 
mature leaf ; its mid-rib st bears the pinnae / / ; at the base 
of one of these is formed the bud Ä', Avhich has also already- 
put out a root (natural size). 
Now that we have already spoken of 
the origin of leaves, hairs, and roots, and 
entered sufficiently into detail on the more important points (Sects. 20, 21, 22), it only 
remains to go a little further into the various modes of origin of leaf-bearing shoots. 
(a) In many Ferns leafy shoots arise from Lea-ves, and especially when the stem 
branches but little or not at all, as in Nephrodium Filix-mas, Asplen'ium Filix-fcßmina, 
Pteris aquilina, &c. In these species the buds spring singly out of the lower parts of the 
petiole at a greater or less height above its insertion. In other species it is usually 
the lamina which produces numerous buds, generally in the axils of the pinnae, as in 
Asplen'ium decussatum (Fig. 127), A. Bellangeri, A. caudatum, Ceratopteris thalictroides, or 
on the surface of the leaf itself, as in Asplen'ium furcatum, &c. In all these cases the 
buds produced on the leaves are exogenous in their origin, and those on the petioles 
of the first-named species arise, while the leaves are still very young, out of single 
superficial cells ^ These shoots take root while still in connexion with the mother-leaf, 
but sooner or later become detached ; in Nephrodium Filix-mas and Pteris aquilina often 
only after some years, when they have already acquired considerable strength, and the 
base of the mother-leaf has died off' and decayed. 
In Phanerogams buds also occur on leaves, although much more rarely. The best 
^ Hofmeister, Beiträge zur Kenntniss der Gefäss-Kryptogamen, vol. IL Leipzig 1857.. 
