20 



CULINARY OR KITCHEN GARDEN. 



or fixed parts of plants. Thus the starch 

 of the seed is changed into the soluble 

 dextrin and sugar of the sap of the young 

 plant, and then again into the insoluble 

 cellular fibre of the stem or wood as the 

 plant grows; and, finally, into the in- 

 soluble starch of the grain, as its seed fills 

 and ripens. They each exercise a chemi- 

 cal action more or less distinct, decided, 

 and intelligible, upon the other elemen- 

 tary bodies, and the compounds of them 

 which they meet with in the sap of the 

 plant. In regard to some substances, such 

 as potash and soda, the sulphuric and 

 phosphoric acids, this last function ap- 

 pears to be especially important. These 

 substances influence all the chemical 

 changes which go on in the interior of 

 the plant, and which modify and cause 

 its growth. The same is true of the 

 nitrogen which the plant contains. This 

 elementary body, in the form of albumen 

 or some other of the numerous protein 

 compounds which occur in the sap, pre- 

 sides over, or takes part in, almost every 

 important transformation which the or- 

 ganic matter of the living plant undergoes. 

 Thus it is always abundantly present where 

 the starch of the seed or of the tuber is 

 dissolved, and sent up to feed the young 

 shoots; and again, when the soluble sub- 

 stances of the sap are converted into the 

 starch of the grain of the tuber, or of the 

 body or pith of the tree, one or other of 

 the protein combinations is always found 

 to be present on the spot where the che- 

 mical change in the transformation is 

 going on. Besides these general func- 

 tions, the several substances found in 

 plants exercise also special functions in 

 reference to vegetable life and growth. 

 Thus— 



" Nitrogen is most abundant in the sap 

 of young plants, takes part in most of the 

 changes of organic compounds which go 

 on in the sap, and fixes itself, as the 

 plant approaches maturity, in greatest 

 abundance in the seeds and in the green 

 leaves. 



" Potash and soda circulate in the sap, 

 influence chemical changes very much, 

 and reside or fix themselves most abun- 

 dantly in green and fleshy leaves, and in 

 bulbous roots. 



"Sulphuric acid is very influential in 

 all chemical changes ; is found, in most 

 cases, in those parts of the plants in which 



potash and soda abound, and deposits a 

 portion of its sulphur wherever the com- 

 pounds of nitrogen form a notable part of 

 the substance of the plant. 



"Phosphoric acid exercises also much 

 influence over the chemical changes of the 

 sap, and finally fixes itself in greatest 

 abundance in the seeds and other repro- 

 ductive parts of the plant. 



"Lime is very important to healthy 

 vegetable growth, as practical experience 

 has long testified. Among other duties, 

 it appears to accompany the phosphoric 

 acid in the sap of plants, and to deposit 

 itself, in combination with organic acids, 

 in the leaves and bark, and with phos- 

 phoric acid in some seeds and roots. 



" Magnesia appears also to attach itself 

 very much to phosphoric acid in the sap, 

 and fixes itself, in combination with the 

 acid, principally in the seed. 



" Chlorine. — The chemical functions of 

 this substance in the sap are less under- 

 stood even than that of the other sub- 

 stances above mentioned. It exists chiefly 

 in combination with soda, and is much 

 more abundantly present in some plants, 

 and in some parts of plants, than in others. 

 Though, as I have said, its immediate 

 chemical functions in the plant are not 

 understood, it forms a most important 

 constituent of the plant, in so far as the 

 after uses of vegetables as ' articles of food' 

 are concerned. 



"Silica exists in the sap in a soluble 

 form, and deposits itself chiefly in the 

 exterior portions of the stems and leaves 

 of plants. It is supposed there to serve 

 as a defence to the plant against external 

 injury, and to give strength to the stem, 

 in the case of the grasses and corn-yield- 

 ing plants ; but what chemical functions 

 it performs, if any, in directly promoting 

 vegetable growth, we can scarcely as yet 

 even venture to guess." 



However extraordinary it may appear 

 to the young cultivator, (and we know 

 many of riper years who scout the idea 

 that plants take up and are in part con- 

 stituted of flint,) yet such is the case; 

 and, moreover, all plants contain mineral 

 matters, such as iron, copper, flint, sul- 

 phur, &c. : if we may venture to hazard 

 a supposition, their presence even in 

 the leaves of the most delicate grass is 

 necessary in the formation of what may 

 be called the bone of the plant ; and no 



