242 MONSTERS ARE STERILE. 



It sometimes happens that particular parts of plants, distant 

 from the fruit, are so constructed as to attract to themselves the 

 food intended for the fruit, and thus to prevent the formation 

 of seed. For example: — The early varieties of Potato do 

 not readily produce seed, owing to the abstraction by their 

 tubers of the nutritive matter required for the support of the 

 seed. Mr. Knight found that by destroying the tubers in 

 part, as they formed, seeds were readily procured from such 

 varieties. 



But perhaps the most frequent cause of sterility is the 

 monstrous condition of the flowers of many cultivated plants. 

 It was explained in Book 1. that the floral organs of plants are 

 nothing more than leaves, so modified as to be capable of 

 performing special acts, for particular purposes ; but they are 

 not capable of performing those acts any longer than they 

 retain their modified condition: and therefore the stamens 

 cannot secrete pollen, when, by accidental circumstances, they 

 are changed into leaves, as happens in double flowers ; in such 

 cases, there is nothing to fertilise the stigma, and, of course, no 

 seed is produced. Or the carpels themselves may be converted 

 into leaves, and have lost their seed-bearing property. Double 

 flowers in the latter case cannot possibly bear seed ; but in the 

 condition first mentioned they may, and often do. To bring this 

 about, the cultivator plants in the vicinity of his sterile flowers 

 others of the same species, in which a part at least of the 

 stamens are perfect, and they furnish a sufficiency of pollen for 

 the impregnation of the other flowers in which there are no 

 stamens. 



In some cases, principally in those of Composite flowers, the 

 seed is formed and advanced towards perfection, and then 

 decays ; this is owing to the flower heads of such plants being 

 composed, in a great measure, of soft scales, absorbent and 

 retentive of moisture, to which, in their own country, they are 

 not exposed in the fruiting season, but by which they are 

 affected under the hands of the cultivator. When the heads of 

 such flowers are soaked with moisture, which they cannot get 

 rid of, the scales rot, decay spreads to aU the other parts, and 

 thus the production of seed is prevented. The Chinese 



