1 78 Climate 



upon ice, and to send out roots into it. Barley and 

 oats will also send out roots with the thermometer 

 down to freezing-point, but they cannot develop seed- 

 leaves without a few degrees of warmth. Maize, as 

 might be expected, requires more heat than any other 

 corn, and will not start until the thermometer shows 

 about 15^° above freezing, and even then grows but 

 slowly; and cucumber-seed shows no sign of life 

 without still more heat. 



But, though many seeds will make a start in cold 

 weather, even in frost, it does not follow that they will 

 do more than start; for a plant requires different 

 degrees of light and heat at different times in its life. 

 And if it does not receive enough at the important 

 period when it has done growing, and is going to 

 blossom, the chances are that it will bear no fruit. 

 For fruit cannot do much towards feeding itself, and 

 though it does take up carbon from the air, it is chiefly 

 dependent for nourishment upon the leaves, the great 

 food manufacturers. But, in a cold summer, the leaves, 

 instead of passing on their stock of food to the fruit, 

 and themselves turning yellow, as they ought to do, 

 seem to be quite thrown out of their calculations. They 

 keep their food to themselves, and remain green and 

 juicy, while the fruit is starved, and its development 

 checked. In very bad cases, the plant puts out new 

 shoots, and the crop never comes to perfection; for 

 the heat which is quite sufficient for the growth of 

 stems and leaves is not sufficient for the growth and 

 ripening of the fruit. 



If, on the other hand, the piant gets too much lignt 

 and heat at an early stage in its life, it grows up and 

 ripens its fruit too quickly, before it is properly 



