BOTANY. 45 
vegetables, as Lichens, Mosses, &c., or upon the bark of living vegetables, 
but do not derive much nourishment from them, as H’pidendrum, Acrides, 
and other orchids, as well as T%llandsia, Bromelia, Pothos, and other air 
plants. 
18. Subterranean Plants, or those which live under the ground, or in 
mines and caves almost entirely excluded from the light, as Byssus, Trufiles, 
and some other cryptogamic plants. 
19. Plants which Vegetate in Hot Springs, the temperature of which 
ranges’ from 80° to 150° Fahrenheit’s thermometer, as Vitex Agnus- 
castus, and several cryptogamous plants, as Ulva thermalis, the hot-spring 
Laver. 
20. Plants which are Deyeloped in Artificial Infusions or Liquors, as 
various kinds of Mucor, causing mouldiness. 
21. Plants Growing on Living Animals, as species of Spheria and 
Sarcinula, and various other Fungi and Algee. 
22. Plants growing on certain kinds of decaying animal matter, such as 
species of Onygena, found on the hoofs of horses, feathers of birds, &c., 
some species of Fungi, which grow only on the dung of animals, and certain 
species of Splachnum. 
There are certain forms of plants which, while occurring within definite 
limits, impart a peculiar character. Meyen, in his Grundriss der Pflanzen- 
geographie, establishes twenty groups as especially characteristic of the 
regions in which they occur. They are as follows: 
1. Gramineous, or Grassy Form. ‘This is illustrated in northern 
countries by meadows and pastures. The cereal grains also have a great 
influence on the aspect of countries. Under this form are included Cype- 
race, Restiacez, and Juncacee. In the torrid zone some arborescent 
forms occur, as Bamboo; and along with these are associated Sugar-cane 
and Rice. Barley is an extra tropical form, while Carex extends to cold 
regions. 
2. Scitamineous Form. This includes the Ginger, Arrowroot, and Plan- 
tain family, some of which attain a large size. They contribute to give a 
character to the torrid zone. 
3. Pandanus, or Screw-pine Form. A tropical form illustrated by Screw- 
pines and Draceenas. 
4, Pine-Apple Form. Illustrated by the Bromeliaceze of warm climates. 
5. The Agave, or American Aloe Form. Chiefly tropical and subtropical. 
6. The Palm Form. Under this are included also the Cycadaceous 
family. They give a character to the hotter regions of the globe. Some 
of the palms are social, as the Date and Cocoa-nut. Chamerops humilis 
represents this form in Europe. 
T. Filical, or Fern Form. True Ferns, in an especial manner, affect the 
landscape in tropical and warm regions. 
8. Mimosa Form. ‘This includes Leguminous plants in general. The 
finely cut foliage of some has a resemblance to Ferns. Modifications of this 
form occur both in warm and cold regions. Acacias, in New Holland, give a 
peculiar feature to the landscape. 
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