SUMMER PLANTS. 41 



flower and produce seed but once present, like the 

 turnip plant, distinct periods of life, as regards the 

 direction of organic activity in them. In the first, the 

 plant produces the organisable matter required in the 

 succeeding period ; in the latter, that which is required 

 for the final functions of life. But these materials are 

 not always stored up in the root, as is the case in the 

 turnip ; in the sago-palm they fill the stem ; in the 

 aloe (Agave) they collect in the thick fleshy leaves. 



The production of seed is, with many of these plants, 

 much less dependent upon any fixed period of time, 

 than upon the store of organisable matter collected in 

 them in the time preceding. Favourable climatic con- 

 ditions or propitious weather will hasten, while unfa- 

 vourable cosmic conditions will retard, its production. 



The so-called summer-plants are monocarps which 

 are able to gather in a few months the conditions re- 

 quired for the production of seed. The oat-plant grows 

 to maturity and bears ripe seed in ninety days; the 

 turnip-rape only in the second year of its existence ; 

 the sago-palm in sixteen to eighteen years ; the aloe in 

 thirty to forty, often not till 100 years. (See Appen- 

 dix B.) 



In many perennial plants, the outer part dies every 

 year, while the root lives on. In the monocarpous 

 plants, the root dies with the production of the seed. 

 In these the production of seed is an indispensable, 

 in the perennial plants more of an accidental, condition 

 of continued existence. 



The economy of plants is regulated by laws which 

 manifest their operation in the peculiar faculty of cer- 

 tain organs to store up food for future use ; so that all 

 the external causes which seem to hinder their develope- 

 ment, actually contribute in the end to insure their 

 continued existence, i.~e. their propagation. 



The contents of the roots .in perennial grasses and 

 asparagus, may, in the different periods of the life of 

 these plants, be compared to the farinaceous body or 

 albumen in the grain of cereals ; with this difference, 

 however, that the skin does not become empty as is the 



