26 THE PLANT. 



produces the organisable matter required in the succeed- 

 ing 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 

 coUect 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. Favom^able climatic conditions or 

 propitious weather will hasten, while unfavourable cosmic 

 conditions will retard, its production. 



The so-called summer-plants are monocarps which are 

 able to gather in a few months the conditions required 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 thhly to forty, 

 often not till 100 years. (See Appendix B.) 



In many perennial plants, the outer part dies every 

 year, while the root fives 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 peren- 

 mal plants more of an accidental, condition of continued 

 existence. 



The economy of plaots is regulated by laws which 

 manifest their operation in the pecuhar faculty of certain 

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

 external causes which seem to hinder their developement, 

 actually contribute in the end to insure theu' continued 

 existence, i. e. then' 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 



