66 PLANT LIFE ON THE FARM. 



than the beardless ones. A variety known as the Blood Ked 

 is very hardy, owing its immunity possibly to its habit of 

 keeping its leaves close to the ground during the winter 

 and spring, and, therefore, less exposed to sudden changes 

 of temperature. In any case, its leaves are more likely to 

 be protected by a coating of snow. The selection, there- 

 fore, of the kind of wheat best adapted for Scotland, for the 

 eastern or for the western counties of England respectively, 

 is a matter of great consequence. A variety which succeeds 

 in a worm moist climate would be quite unsuitable for a 

 drier one, even if the temperature sometimes rose higher. 



In moist air it has lately been shown by M. Vesque that 

 the leaves are both thinner and longer than when grown in 

 dry air, that the vascular bundles of the stem are also 

 thinner, and less perfectly developed than in dry air. Thus, 

 the effects of a saturated atmosphere on the growth of 

 leaves seem to be very similar to those mentioned by 

 Rauwenhof as characteristic of plants grown in obscurity. 

 When fully exposed to the light, in a dry, hot, stagnant 

 atmosphere, where transpiration fromthe surface of leaves 

 is ample, the leaves become thicker, their anatomical 

 structure is altered, and they show a tendency to become 

 more hairy. 



It would not be worth while for the agriculturist to try 

 and make his plants adapt themselves to different conditions 

 as the experimentalists and physiologists do, but the indi- 

 cations and facts brought forward by the latter may very 

 profitably influence the farmer's selection of the particular 

 varieties best suited, by their conformation or structure, to 

 meet the vicissitudes of particular localities. 



The Influence of Contact on Leaves This may be 



