PROTECTION OF BUDS 451 



Smith, 19 1 3) as the basis of a classification of the " life 

 forms " or " biological types " of plants. He distinguishes 

 between : Phanerophytes, trees and shrubs with exposed 

 dormant buds on branches projecting into the air ; Chamce- 

 phytes, with buds on shoot apices on, or just above, the soil 

 surface, such as Empetrum nigrum, or Stellaria Holostea ; 

 Hemicryptophytes, with dormant buds in the upper crust 

 of the soil, the aerial parts herbaceous and dying away, e.g. 

 Mercurialis perennis, Chrysanthemum Leucantheniuni ; rosette 

 plants may be included here or in the foregoing class ; 

 Geophytes with subterranean buds, as in the bulbous 

 or tuberous plants ; in the helophytes (marsh plants) 

 and hydrophytes (water plants) buds may be found on 

 perennating rhizomes in the mud, or special detached buds 

 (turions) may be formed, as in the bladderworts ; Thero- 

 phytes, which live through the unfavourable season as seeds. 

 There are one or two other classes which need not concern 

 us here, and some of those mentioned are subdivided. 

 Raunkiaer has used the distribution of the species of a flora 

 among his different classes to construct a " biological 

 spectrum," the nature of which is characteristic for different 

 climates. Thus, to take instances which illustrate points 

 already mentioned in this section, it is shown that the 

 therophytes and small phanerophytes predominate in arid 

 regions, e.g. Nevada ; the chamaephytes, hemicrytophytes, 

 and geophytes in climates with a cold winter, e.g. Labra- 

 dor ; the phanerophytes in the moist regions of the tropics, 

 e.g. West Indies. Different regions of a small area and 

 different altitudinal zones may show characteristically 

 different spectra. 



Leaf-fall and Rhythm. — The periodic climatic change 

 is related to a rhythmical vegetative change very con- 

 spicuous in our woods with their autumnal leaf-fall, their 

 winter rest, and their spring awakening. At first sight 

 it seems as if the fall of the leaf were directly due to the 

 storms and early frosts of autumn, and the winter rest to 

 the short, cold day. The relation is in reality not nearly 

 so simple. The fall of the leaf is definitely prepared for 



