150 
MORPHOLOGY OF MEMBERS. 
the green organs which have been termed simply leaves (foliage-leave§). All 
these structures are therefore also called Leaves {Phyllomes) ; and this designa- 
tion is frequently justified by the fact that many of these organs actually become 
transformed, under peculiar conditions, into green leaves. Since the green organs 
which are termed leaves in popular language (foliage-leaves) may be considered 
as leaves par excellence, the other structures, which are also considered to be 
foliar, are termed me/amofphosed leaves. The same is also the case with those 
parts to which the leaves are attached, and on which they grow as lateral ap- 
pendages. They sometimes have the form of cylindrical or prismatic, slender, 
greatly elongated stems, sometimes of thick roundish tubers, or are often hard 
and lignified (trunks) ; in other cases they are soft and flexible, either embracing 
other firm bodies (bines), or firmly attached to them, as in the ivy; they may 
also occur as sharp spines or tendrils (grape-vine). All this is connected with 
the mode of life of the plant, and with the functions of the structures under 
consideration. But if the one characteristic only is kept in view, that they all bear 
leaves which arise below their growing apices, an agreement is found as important 
as complete, which may for the time be altogether abstracted from the physio- 
logical functions and the corresponding structure ; and when once this abstraction 
is made, the agreement may be denoted by applying a common name to all those 
parts which bear leaves; they may be termed Stem-structures ifiaulomes) or simply 
Axes. In the same sense therefore in which, for example, the tendril of a pea is a 
leaf, the tuber of a potato is also a stem or axial structure ; and just as the tendril of 
a pea is termed a metamorphosed leaf, so the tuber of a potato may also be called a 
metamorphosed stem. 
The same is the case with hairs as with leaves and stems ; the distinguishing 
characters of root-hairs, woolly hairs, prickles, glandular hairs, &c., is that they all 
originate as outgrowths of epidermal cells. If we now go a step further, we may term 
all appendages of other parts which originate as outgrowths of epidermal cells, 
whatever their form and function. Hairs {Trichomes). Thus the so-called palese and 
the sporangia of Ferns are trichomes ; or, if the ordinary filiform hairs are considered 
the original form, they are then metamorphosed hairs. It does not necessarily follow 
that hairs grow from a true epidermis ; it is held sufficient if they arise from single 
superficial cells ; and thus the number of the external appendages termed trichomes 
is still further increased. 
As in the case of stems, leaves, and hairs, we may speak also of metamorphosed 
roots ; they are usually filiform, long, and slender, but sometimes thick and tuberous ; 
usually they grow beneath the ground, but also sometimes above ground, and even in 
an upward direction. Nevertheless, under all circumstances roots maintain so striking 
a similarity to their typical forms, that the term metamorphosed is but seldom ap- 
plied to them. 
This mode of ifivestigation, applied to Vascular Cryptogams and Phanerogams, 
has shown that all the organs of these plants may be referred to one of these 
morphological categories ; every organ is either Stem (Axis), Root, Leaf, or Hair. 
The Muscinese have no roots in a morphological sense, although they possess 
organs which completely fulfil the functions of roots ; on the other hand most have 
leaves which grow on stems (axes). In Algae, Fungi, and Lichens, the plant has 
