RADICATIOX OF DIFFERENT PLANTS. 13 



grass (Lolium) puts forth root-suckers in a stiff soil, and 

 prostrate stolons in loose ground. Cat's-tail grass (Phleinn) 

 is found sometimes with bulbous, sometimes with fibrous 

 many-headed roots, having a tendency to creep and to 

 form mother-stocks. Timothy-grass grows stalk in the 

 first year ; in the second, it forms sometimes bulbous, 

 sometimes fibrous many-headed mother-stocks, which send 

 forth creepers in all directions. In the same way, 

 meadow-grass spreads partly by budding suckers, partly 

 by stolons. 



On comparing the vital processes in annual, biennial, 

 and perennial plants, Ave find that the organic work in 

 perennials is principally directed to the formation of the 

 root. 



The seed of asparagus sown during autumn, in a fertile 

 soil, will produce next year, from spring to the end of 

 July, a plant about a foot high, the stem, twigs, and 

 leaves of which from that time forward show no further 

 increase. The tobacco plant, which is an annual, Avould 

 from the same period to the end of August have pro- 

 duced a stem several feet high, covered with numerous 

 broad leaves ; and the turnip a broad crown of foliage. 



But the cessation in the growth of the asparagus plant 

 is only apparent ; for from the moment that the external 

 organs of nutrition are developed, the root increases in 

 extent and substance in far greater proportion to the over- 

 ground organs than is the case with the tobacco plant. 

 The food which the leaves have absorbed from the air and 

 the roots from the soil, having first been transformed 

 into organisable matter, descends to the roots, in which 

 there is gradually collected a suflicient store to enable 

 the latter to furnish in the following year from themselves 

 and without the least supply of food from the atmosphei'e 

 the material required for the production of a new perfect 



