366 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



the full purport of which is still by no means fully understood. 

 Other species of the genus, as also the allied Darlingtonia 

 of California, manifest the same purpose of insect-capture, 

 whatever the final object may be. 



PHYSIOLOGICAL CLASSIFICATION OF PLANTS. 



A classification of plants, based upon physiological char- 

 acters and their relations to climatic conditions, has been re- 

 cently proposed by M. A. de Candolle, and discussed with 

 special reference to its bearing upon the study of the vegeta- 

 tion of the globe in past ages. He divides plants into six 

 groups, sufficiently well characterized within general limits, 

 of which the first includes plants requiring a large amount 

 of heat and moisture, such as are now found in the hot, damp 

 valleys of the tropics, where the mean temperature exceeds 

 86 Fahr., and moisture is never wanting. These he desig- 

 nated as Megatherms mainly woody plants and evergreen 

 climbers, including forest trees of numerous species growing 

 together, and air-plants in comparative abundance. Fossil 

 remains show that at a very early period a flora of nearly 

 identical character was distributed over a large part of the 

 globe, but since the beginning of the tertiary era it has be- 

 come limited more and more closely to the equatorial regions. 



The second group (Xerophiles) requires as much heat but 

 less moisture, occupying the dry regions from Southern Cal- 

 ifornia east and southward, certain portions of South Amer- 

 ica, and in the Old World from the Senegal to Arabia and 

 the Indus, Australia, South Africa, etc. It includes few trees, 

 but many shrubby or herbaceous perennials, and numerous 

 succulent plants. The third group of Mesotherms requires a 

 more moderate degree of heat (a mean of 58-68 Fahr.) and 

 of moisture, and comprises much of the flora of the Southern 

 States, California, China and Japan, New Zealand and Tas- 

 mania, the Mediterranean region, and the like, including a 

 great variety of orders. A similar flora existed during the 

 early tertiary period in Spitzbergen and much of North 

 America, the vegetation of the United States and Japan be- 

 ing then nearly identical. The fourth group (Microtherms) 

 is limited by a mean temperature of 32-58 Fahr., and is 

 characterized by the abundance of deciduous trees, conifers 

 (the forests often formed by trees of but a single species) 



