30 THE PLANT. 



further increase. The tobacco plant, which is an an- 

 nual, would from the same period to the end of August 

 have produced 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 in- 

 creases in 'extent and substance in far greater propor- 

 tion to the over-ground organs than is the 'case with 

 the tobacco plant. The food which the leaves have ab- 

 sorbed 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, 

 sufficient store to enable the latter to furnish in the fol- 

 lowing year from themselves and without the least sup- 

 ply of food from the atmosphere the material required for 

 the production of a new perfect plant, with a stem half 

 as high again and a much greater number of twigs and 

 leaves. The organic labour of this new plant, during 

 the second year, results in the generation again of 

 products which are deposited in the root, and, propor- 

 tionately to the greater extent of the organs of nutrition, 

 are stored up in much greater quantity than the roots 

 had originally supplied. 



The same process is repeated in the third and fourth 

 years ; in the fifth and sixth years the store deposited 

 in the roots has become sufficiently rich to produce in 

 spring, when the weather is warm, three, four, and 

 more stems as thick as a finger, with numerous branches 

 covered with leaves. 



A comparative examination of the green asparagus 

 plant, and of its withering stems in autumn, seems to 

 indicate that at the end of the period of vegetation the 

 remainder of the dissolved or soluble substances fit for 

 future use, then still remaining in the overground 

 organs, descend to the root. The green parts of the 

 plant are comparatively rich in nitrogen, alkalis, and 

 phosphates, whilst in the withered stems these sub- 

 stances are found in small quantities only. The seeds 



