BOTANY. 45 



vegetables, as Lichens, Mosses, (fcc, or upon the bark of living vegetables, 

 but do not derive much nourishment from them, as ßpidendrum, Aerides, 

 and other orchids, as ^vell as Tillandsia, 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 Byssas, Truffles, 

 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 Ag7ius- 

 castus, and several cryptogamous plants, as Ulva thermalis, the hot-spring 

 Laver. 



20. Plants which are Developed in Artificial Infusions or Liquors, as 

 various kinds of Mucor, causing mouldiness. 



21. Plants Growing 07i Living Animals, as species of Sphcsria and 

 Sarcinula, and various other Fungi and Algas. 



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 Pfianzen- 

 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- 

 raceae, Restiacese, and Juncacese. 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 Dracaenas. 



4. Pine- Apple Form. Illustrated by the Bromeliaceee 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. Chainoirops humilis 

 represents this form in Europe. 



7. Filical, or Fern Form. True Ferns, in an especial manner, aflect 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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