HOLE : SOME INDIAN GRASSES AND THEIR CECOLOGY. 31 



of vegetation found in their forests and also so far as possible ascertain and record the 

 condition of the environmental factors existing in the various habitats. As regards the 

 cecology of the principal species, also, it is particularly desirable to record careful notes on 

 such points as the periods of vegetative activity, of flowering and fruiting, the agencies by 

 which flower pollination and seed distribution are effected, the time when the seed naturally 

 germinates and the factors which appear of special importance in effecting the development 

 of the young plants during the first few years of existence, as on all these points the main- 

 tenance or extension of the area occupied by a particular species, or type of vegetation, 

 largely depends. 



29. It is a remarkable fact that, although the importance 

 value of the study of mycology and entomology in helping us to secure the healthy develop- ° n St „,° y g Jt 

 ment of our valuable plants is fully recognised, the dominating importance of physiology nisXses. 

 and oecology is frequently lost sight of and the view is not infrequently held that most plant- 

 diseases of importance are caused primarily by either fungi or insects. 



Every plant-physiologist however is aware of the vital importance to plant-life of such 

 primary factors as the available moisture supply, the degree of soil aeration, the tempera- 

 ture, light and competition of other plants and knows that even slight variations in these 

 factors are able to cause disease and death. Notwithstanding this, we have, as yet, no 

 precise knowledge (in the case of any single Indian tree of importance) as to the degree of 

 intensity at which such factors first begin to cause disease and when they must accordingly 

 be considered injurious. 



It is important to note, also, that an accurate knowledge of such factors offers every 

 prospect of producing practical results of value, seeing that the intensity of these factors 

 can be altered within considerable limits by the ordinary operations of practical forestry 

 and thus those conditions may be produced which are necessary for the healthy development 

 of particular plants in cases where such conditions do not exist, or have been destroyed by 

 careless management. Thus the water content of a sandy soil may be increased and its 

 aeration diminished by introducing a species with considerable power of humus production 

 such as Adhatoda Vasica, the aeration and texture of a heavy soil may be improved by 

 introducing a species capable of withstanding poor soil-aeration and of producing a good 

 humus supply, temperature can be altered by a judicious use of shelter-woods and by 

 arranging fellings so as to secure good circulation of air, while plant competition may be 

 controlled by introducing factors such as periodic fires which are unfavourable to the com- 

 peting plants. On the other hand it is a remarkable fact that, although mycology and 

 entomology are able in many cases to suggest effective remedial and preventive measures 

 which are applicable in agriculture, horticulture and arboriculture, such measures can 

 rarely be adopted in practical forestry, especially in countries where the general value of 

 the produce is small and the forest management not intensive. Frequently the only remedy 

 is to cut out the affected trees and in bad cases to change the species, which is often a 

 lengthy and difficult operation, while the new species is frequently less valuable than the 



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