^64 American Horticultural Society. 



Apple trees in eight years have been found to send out roots horizontally 

 twenty feet from the trunk ; a Concord grape-vine in two years produced a 

 root which was followed thirteen and a half feet; a Lombardy poplar devel- 

 oped roots in abundance beneath an old woody;trd seventy five feet distant 

 from the trunk. In New Hampshire the living roots of an elm are authori- 

 tatively said to have blocked a dr dn tile 400 feet from the base of the tree I 

 Whatever may be said of this last, the others are vouched for by myself, and 

 were observed when the subject was under investigation, so that the closest 

 examinations were made and mistakes rendered improbable, if not impos- 

 sible. 



One thing further needs to be noted, viz.: that the roots of most land- 

 growing plants are not only fitted for the absorption of moisture from soil 

 without free water, but do their best work when there is visible water about 

 them. In most such cases plants sutler when their roots are immersed in 

 standing water. Among other injuries, the root hairs perish. The roots of 

 purely aquatic plants have no root hairs. 



The next substance in order of quantity in the structure of plants is car- 

 bon. This composes nearly one-half the weight of the dried wood. We see 

 it retaining the perfect shape and size of the original structure in carefully- 

 prepared charcoal. In the manufacture of the latter the water in the two 

 states above described is expelled and the carbon alone retained. The 

 amount, though by no means so great a proportion of the green plant as is 

 composed of water, is in the aggregate very large. For every ton of green 

 wood we may estimate about one-fourth or five hundred pounds of carbon. 

 Vegetation gives us the only supply we have of this material in the free 

 state ; the coal dug from the earth is only the preserved carbon of former 

 plant growths. Even plumbago and the diamond are believed to owe their 

 origin to the assimilative activities of green plants. 



This substance is obtained by the living plant in the shape of carbonic 

 acid, and is for the most part absorbed by the leaves from the atmosphere, 

 in which it is constantly present, and upon an average constitutes four parts 

 in every ten thousand parts of the gaseous envelofje of the earth. It also 

 enters the roots, being absorbed to some extent in W'ater,and thus ultimately 

 gains the leaves, where at all events it must go before becoming of service to 

 the plant &=>■ food. The process called assimilation in the green parts, 

 under the infiuence of light, is the one striking and characteristic phenom- 

 enon of vegetation. In this process the carbonic acid is separated into its 

 constituent elements, carbon and oxygen, the former retained and the latter 

 given off to the air. As there is a strong chemical aflfiiity between these 

 elements, an expenditure of force is required for their disassociation, and 

 this force is believed to be furnished by the sun. Man, however, has not yet 

 been able to imitate the leaf in directly utilizing after this method the light 

 and the heat sent freely upon us. Possibly he may learn how some day, and 

 be able to set up a manufactory of starch out of carbonic acid and water; 

 thus making food for himself from the abundant supply of the air and of a 



