VEGETABLE PHYSIOLOGY. 



ould be made of the quantity of inorganic 

 matter present in hay or grass, from a know- 

 ledge of its weight in the green state only. The 



VEGETABLE PHYSIOLOGY. 



annexed quantities are contained in 1000 Ibs 

 of the dry haj of each plant : 



VEGETABLE PHYSIOLOGY is that sci- 

 ence which treats of the vegetable kingdom, its 

 habits, properties, and organization, in the most 

 comprehensive manner. Its object.* have been 

 clearly stated by Mrs. Marcet, in her excellent 

 CWma/ioM on Vegetable Physiology, when de- 

 scribing the lectures of M. Decandolle on this 

 science, and what she has so well described, 

 it is needless lor me to give in other words. 

 "80 far from confining himself to the classifi- 

 cation of plants, the physiologist examines the 

 vegetable kingdom in its most comprehensive 

 and philosophical point of view. In describing 

 Ihe structure, he investigates the habits and 

 properties of plants, and shows, not only how 

 wonderfully they have been formed to fulfil the 

 purposes of their own multiplication and pre- 

 servation, but how admirably they answer the 

 high purpose which nature has assigned to 

 them, of ministering to the welfare of the ani- 

 mal creation, and more especially to that of 

 man. He turns his attention particularly to 

 nt the means by which the science of 

 botany can promote that with which it is most 

 intimately and importantly connected agricul- 

 ture. He makes ready the soil and sows the seed 

 for the husbandman ; he extracts the healing 

 juices and the salutary poisons for the physi- 

 cian; he prepares materials for the weaver, co- 

 lours for the dyer : in a word, as he proceeds, 

 there is scarcely an art on which he does not 

 confer some benefit, either by pointing out a 

 new truth, or warning against an old-establish- 

 ed error." From this description of the objects 

 of the science of vegetable physiology, the 

 reader will see that almost all its different 

 branches are treated of separately in articles 

 which are dispersed through this volume. It 

 is only, therefore, a few scattered fragments 

 rhich I propose to gather together in this 

 place. See ACCUMATIOH, BOTAJTT, EAUTHS, 

 GAMS, LIOHT, PUTREFACTION, SALTS, TEMPE- 

 BATTHK, WATER, Ac. 



The description of the cambium for the de- 

 scending sap of plants was omitted in its pro- 

 per place, and the effect of gravity or attrac- 

 tion upon plants was referred to this head. 

 e sap having ascended into the leaves, and 

 being in its course gradually altered into a 

 luid suitable ibr the nourishment of the plant, 

 descends principally through the liber, or inner 



yer of bark, but a small portion also descends 

 through the young wood, or alburnum. This 

 movement, especially through the plants with 

 "> 



pendent branches, is materially facilitated by 

 motion, as by the action of the wind. " Mr. 

 Knight," adds Mrs. Marcet, "has made a va- 

 riety of interesting experiments on this subject. 

 He confined both the stem and branches of a 

 tree in such a manner that it could not be 

 moved by the wind. The plant became feeble, 

 and its growth much inferior to that of a 

 similar tree growing in its natural state. He 

 confined another tree so that it could be moved 

 only ]jy the north and south winds, and ob- 

 tained the singular result of an oval stem, the 

 sides accessible to the wind growing more 

 vigorously than those sheltered from its influ- 

 ence. Every species of restraint, and espe- 

 cially such as tend to render plants motion- 

 less, impedes their growth. Stakes by which 

 young trees are propped, nailing them to walls 

 or trellises, green-houses, or confined situations 

 where the air has not free access, check and 

 injure the vigour of vegetation, and render 

 plants diminutive and weakly. The cambium 

 descends almost entirely through the liber or 

 most internal and youngest layer of the bark; 

 if, therefore, a ring is cut completely through 

 the bark, this fluid is arrested in its course, 

 and, accumulating around the upper edge of 

 the intersected bark, will cause an annular pro- 

 tuberance. The descent of the cambium thus 

 being obstructed, it will accumulate in that part 

 of the tree above the intersection, afford it a 

 superabundance of nourishment, creating a 

 proportional vigour of vegetation, and a cor- 

 responding excellence and profusion of pro- 

 duce." This operation, or ringing, is often per- 

 formed on the non-productive branches of fruit 

 trees. 



The effect of gravitation or attraction upon, 

 plants is of the highest importance to their ger- 

 mination and their growth. From the very 

 nature, however, of this essentially present 

 power, a principle known only to us by its 

 effects, the research is surrounded with diffi- 

 culties. Mr. Knight, the late excellent presi- 

 dent of the Horticultural Society, described 

 some of the effects of gravity upon plants in 

 his usual happy manner, when, in addressing 

 the fellows of the Royal Society, he observed, 

 "It can scarcely have escaped the notice of the 

 most inattentive observer of vegetation, that in 

 whatever position a seed is placed to germi- 

 nate, its radicle invariably makes an effort to 

 descend towards the centre of the earth, while 

 the elongated germen takes precisely the oppo- 



