Vol. X, No. 2.] Leaf Structure of Zoysia pungens, WiUd. 51 

 [N.S.] 



Ihe temperature of the sandy beach at Madras may be 

 taken as 90 F or 32°C roughly on an average. Wnen deal in 



with temperature, we should also consider tha temperature of 

 the particular soil. Under tli3 influence of the sun's rays, the 

 temperature of at least the superficial layers of the soil rises t<» 

 somewhere near the maximum limit. This intense surrounding 

 heat is not altogether favourable to the well-being of the plant 

 Vegetable physiologists have experimentally proved that warm- 

 ing the soil is attended by an increase in the absorption of 

 water and transpiration. Protective contrivances are therefore 

 called for and an investigation show their actual existence. 



Light. — This is one of the most important external factor > 

 affecting plant form and structure. Whilst temperature has 

 no great influence in determining a plant s conformation, light 

 on the other lv-ind plays a prominent part in controlling the 

 structure of plants. The effects of light depend not on the 

 amount but on the degree of its intensity. For instance, 

 very intense light acts fatally on the protoplasm, while 

 subdued, diffuse light acts somewhat beneficially to it. In 

 vegetable organisms, death occurs from too intense a light 

 indirectly owing to the decomposition of pigments primarily 

 associated with assimilation, but at any rate land plants, 

 owing to intense illumination, suffer from a considerable dis- 

 integration of their chlorophyll. The importance of the 

 chlorophyll corpuscles to plant-life is too well known to be 

 mentioned here. These chlorophyll corpuscles are so extremely 

 sensitive to varying degrees of light that they frequently re- 

 arrange themselves. The slightest variation in the light affects 

 them considerably. On the sea-shore, the plant is actually 

 exposed to a glaring sunlight nearly throughout the day. How 

 then are the chlorophyll corpuscles carrying on their work ? 

 The answer is simply that there must be certain adaptive 

 true tu res playing the part of light-regulators. 



Air. — The influence of the wind on plants is partly direct 

 by its stret hing action and by pressure and partly indirect by 

 increasing transpiration. It may of course be doubted whether 

 these will affect such small creeping plants as the present 

 one. The injury, in this case, will not be much by .stress, or 

 pressure, but the continuously blowing wind wi 1 cause an 

 excessive increase of transpiration. Again, the purely mechani- 

 cal disturbance of shaking, due to winds, stimulates the 

 protoplasm in such a way as to increase transpiration. On the 

 sea shore, continuous and violent winds are constantly occur- 

 ring. Consequently, the plants growing there freely should 

 possess some adaptations to combat successfully with the 



above-mentioned injurious influences. 



Peculiarities due to the action of the agencies indicated 

 above next claim our attention. Adaptations in relation to 

 the above environmental conditions are combined in the 



