IN FALLING LEAVES. 227 



The principle is one of economy. The processes are those 

 which effect (i) the avoidance of loss of valuable material; 

 (2) the actual removal of an organ no longer profitable to the 

 tree ; (3) the protection of the tree from injury at the points of 

 removal. 



We will glance briefly at these, concerning ourselves now only, 

 of course, with trees which we know as " deciduous." Everyone 

 understands to-day how entirely the vegetable world is dependent 

 upon Chlorophyll. Thanks to the modern diffusion of scientific 

 knowledge, there are but few who have no idea of this fact. Not 

 everyone, however, apprehends in this connection the supreme im- 

 portance of leaves to the tree that bears them. That they are the 

 true functional representatives of both lungs and stomach, is a fact 

 only dimly grasped by very many of those who are " fond of 

 flowers." Nor would they probably be disposed at first to admit 

 that the leaf is a more highly organised structure than the flower, 

 and of much more value to the parent organism. Yet so it is, 

 though here we must assume rather than stay to prove. 



Now, we are almost all aware that a certain temperature must 

 be maintained in the animal stomach, if digestion is to take place 

 happily. The exception is apparently found in the case of those 

 who flood themselves inside with cold water by way of com- 

 mencing dinner. A better prescription for the sure acquisition of 

 dyspepsia could hardly be invented. And the harm is not, as is 

 sometimes thought, in the "dilution of the gastric juice," but in 

 the reduction of the temperature. Thus Dr. Beaumont observed 

 that the introduction of a single gill of water at 50^ F. into the 

 stomach lowered its temperature upwards of 30°, and its natural 

 heat was not restored for more than half an hour. And when a 

 bottle containing food and gastric juice — easily digested at loo*' 

 F. — was exposed to cold air, scarcely any digestion at all took 

 place. So much for the practice — as sensible as many other 

 items of fashion — of taking ice and iced cold water with a meal. 



To return to Chlorophyll. It is found that its important 

 functions can only be discharged at a temperature varying between 

 6° — 40? C, or 40° — 90^ F. This manifestly requires direct 

 sunlight, and an absence of cold winds, frost, etc. Now, what- 

 ever doubts we may have concerning to-morrow's weather, we 



