CONSUMPTION IN FLOWERING. 211 



by the Agave, or Century-plant, so called because it flowers in 

 our conservatories only after the lapse of a hundred, or at least a 

 great number of years ; although, in its native sultry clime, it 

 generally flowers when five or six years old. But whenever this 

 occurs, the sweet juice with which it is filled at the time (which 

 by fermentation forms pulque, the inebriating drink of the Mexi- 

 cans) is consumed at a rate correspondent to the astonishing rapid- 

 ity with which its huge flower-stalk shoots forth (24), and the whole 

 plant inevitably perishes when the seeds have ripened. So, also, 

 the Corypha, or Talipot-tree, a magnificent Oriental Palm, which 

 lives to a great age and attains an imposing altitude (bearing a 

 crown of leaves, each blade of which is often thirty feet in circum- 

 ference), flowers only once ; but it then bears an enormous num- 

 ber of blossoms, succeeded by a crop of nuts sufficient to supply 

 a large district with seed ; while the tree immediately perishes 

 from the exhaustion consequent upon this over-production. 



370. Flowering and fruiting, then, draw largely upon the plant's 

 resources, while they give back nothing in return. In these opera- 

 tions, as also in germination, vegetables act as true consumers (like 

 animals, 363), decomposing their own products, and giving back 

 carbonic acid and water to the air, instead of taking these materials 

 from the air. It is in flowering that they actually consume most. 

 In fruiting, although the plant is robbed of a large quantity of nour- 

 ishment, this is mostly accumulated in the fruit and seed, in a con- 

 centrated form, for the future consumption, not of the parent plant, 

 but of the new individual inclosed in the seed. As we may treat 

 of the latter elsewhere, we have here to contemplate only the real 

 and immediate consumption of nourishment by the flower. 



371. This is shown by the action of flowers upon the air, so dif- 

 ferent from that of leaves. While the foliage withdraws carbonic 

 acid from the air, and restores oxygen (346, 358), flowers take a 

 small portion of oxygen from the air, and give back carbonic acid. 

 While leaves, therefore, purify the air we breathe, flowers con- 

 taminate it ; though, of course, only to a degree which is relatively 

 and absolutely insignificant. 



372. Evolution of Heat, When carbon is consumed as fuel, and 

 by the oxygen of the air converted into carbonic acid, an amount of 

 heat is evolved, directly proportionate to the quantity of carbon con- 

 sumed, or of carbonic acid produced. Precisely the same amount 

 is more slowly generated during the gradual decomposition of the 



