6 



INDIAN FOREST MEMOIRS. 



it is likewise water that plays the leading part in determining the creation of plant com- 

 munities and their distribution over the soil." 1 He accordingly classifies plants into — 



SSSC I-r-Wafe*. or Aquatic- 

 Mesophytes. Plants = Hydrophytes 



" Plants that pass the 

 whole or the greater 

 part of their lives sub- 

 merged in the water, 

 which envelops them 

 completely or, at most, 

 leaves definite floating 

 parts of them un- 

 covered at its sur- 

 face/' 2 



II. — Land or Terrestrial- 

 Plants 



Those " that expose at least 

 their assimilating organs to 

 the air and hence to trans- 

 piration.''' 3 Those are sub- 

 divided into — 



(a) Xerop/zytes. — " Th o s e 

 species that are adapted 

 to meet the conditions 

 of strongest transpira- 

 tion and most precari- 

 ous water supply.'" 



(b) Mesophytes. — " The re- 



mainder." 4 



It is, however, pointed out that there is no sharp boundary between these groups " for 

 there is a group of plants, marsh-plants (helophytes), which, like water-plants, develop 

 their lower parts (roots, rhizomes, and, to some extent, leaves) in water or at least in soaking 

 soil, but have their assimilatory organs mainly adapted to existence in air, as is the case 

 with land-plants to which they are closely allied," 5 while " between these two classes 

 (ocerophytes and mesophytes) there is of course no strict boundary." 15 It should be noted 

 that while Warming includes marsh plants in terrestrial plants, 7 Clements classes them 

 as hydrophytes. 8 For the present these plants may conveniently be considered as Hydro- 

 phytes. 



Some idea of the kind of plants included in the above groups will be obtained from 

 the following enumeration of a few of the more obvious characteristics of some typical 

 plants : — ■ 



Hydrophytes including Marsh plants. 



Roots are usually reduced. Root-hairs often absent. Owing to the buoyancy of water 

 there is comparatively little need of strengthening mechanical tissue and submerged 

 plants include no woody species. Owing to the slow diffusion of oxygen in water, all sub- 

 merged parts of plants are especially liable to the dangers of an insufficient oxygen-supply 

 for respiration and in consequence large and abundant air spaces in such parts are very 

 characteristic and serve for the storage of oxygen and for the conduction of this gas from 

 parts in the air to those in the water or saturated soil. The presence of these air spaces 

 can often be detected by the naked eye. 



1 I.e., p. 96. 



2 „ p. 96. 

 8 „ p 97. 



4 „ p. 101. 



s ,. p. 131. 



R „ p. 101. 



7 „ p. 97. 



6 Plant Physiology and Ecology by P. E. Clements, 1607, p. 165. 



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