evil. — THE WALL PENNYWORT. 
Cotyledon Umbilicus-Veneris Linne. 
I T is by no means safe to infer the conditions under which a plant grows from its 
general habit or structure. It not infrequently happens that an extensive group 
of plants, perhaps a whole Family, may inherit certain striking external characteristics 
which were originally adaptive, while individual members of the group have acquired 
a secondary adaptation to an altogether different set of conditions. 
Thus the glabrous, and often glaucous, fleshy leaves of the Crassulace^e suggest 
xerophilous conditions ; and, for the majority of the members of the Family, this 
suggestion is an accurate indication of the dry environment in which they live. It 
is not so, however, for the Wall Pennywort {Cotyledon Umhilicus-Veneris Linn6), 
which, though sometimes to be found on dry stone walls in the dry air of our eastern 
counties, is far more abundant and more luxuriant on wet rocks and banks in the 
moister air of the south-west. So too the storing up of nutriment by perennial 
plants in enlarged rounded underground structures, whether bulbs or corms, is 
more frequent among plants inhabiting very dry situations ; but in this Wall 
Pennywort we find a round, solid underground stem sending out a few fibrous 
adventitious roots thickly covered with root-hairs and producing successive 
internodes upwards very much as in Crocus. 
The genus Cotyledon is now a considerable one, numbering some ninety species, 
since it has been found impossible to keep separate from it the plants formerly known 
as Echeverici, many of which are familiar in gardens and green-houses. The main 
botanical characters of the genus, in addition to those common to the whole Family, 
are the presence of five parts in each floral whorl, the union ot the five petals into a 
tubular or bell-shaped corolla, and the epipetalous insertion of the stamens. The 
character, however, to which the group owes its generic name and most of its 
popular appellations is one that is not even universal within the limits of a single 
species, viz. the orbicular peltate leaves. Herbert Spencer, writing, as few botanists 
have ever written, of the pure science of morphology, cites, in his “ Principles of 
Biology,” the leaves of Cotyledon Umbilicus-Veneris as an example of different kinds of 
symmetry occurring in the leaves of the same plant, along with differences in their 
relations to conditions, and illustrates his remarks by a graphic little sketch. 
“ The root-leaves,” he says, “ that grow up on vertical petioles before the (lower-stalk makes its appearance, are 
symmetrically peltate 5 while the leaves which subsequently grow out of the (lower-stalk are at the bottom transitionally 
bilateral, and higher up completely bilateral.” 
Dioscorides called the plant kotuXtjSwi', kotuledon, from kotuXt), koiule, as 
some early Latin writers called it Acetabulum., the words kotvXt) and acetabulum both 
meaning alike a round dish or bowl, the hollow dish-like socket of the hip-joint 
or other similar hollows in other parts of the body. Matthioli called it Umbilicus 
Veneris from the same character ; whilst the great Flemish botanist Charles de 
