Physiology of Plants. 269 



REVIEWS. 



Art. I. The Physiology of Plants, or the Phenomena and Laws of Vegetation. 

 8vo, 298 pages. London, 1833. 



This very interesting little volume is, we believe, by Mr. Murray, whose 

 Manual of Chemistry was noticed in IX. 607. The work is divided into thirteen 

 chapters, which treat of the distinction between animal and vegetable being, 

 the composition of the plant, the root, the stem, the blossom, seeds, the phe- 

 nomena of germination, the ascent and circulation of the sap, the peculiar 

 secretions of plants, the condensation and retention of moisture by trees, 

 parasitic vegetation, extremes of temperature in relation to vegetation, aquatic 

 vegetation, purification of the atmosphere, eccentricities of plants, relations of 

 light and electricity to plants, age of* plants, &c: and, under these heads, the 

 work contains a mass of interesting facts and phenomena in relation to vege- 

 tation, from the germination of the seed to that period when, deprived of the 

 animating principle, the plant becomes the subject of that purely chemical 

 agency which finally accomplishes its total decomposition. 



As the excretory organs of plants are now engaging the attention of several 

 of your correspondents, it may not be out of place to give the author's ideas 

 upon the subject : — "In a variety of experiments made with the hyacinth 

 raised in a bulb glass, and supplied with distilled water, I constantly found 

 that the water in which the fibrils were extended became soon impregnated 

 with carbonic acid gas, when excluded from all external sources of its produc- 

 tion ; and, by the addition of a little lime-water in the first instance, I some- 

 times had an interesting deposition, on the sides of the glass, of minute rhom- 

 boidal crystals of transparent carbonate of lime. It seems to me, therefore, 

 that the functions of the root are twofold, and that it is composed of two 

 classes of organs, one of which act as absorbents, and the other as excretory 

 vessels : the former appear to be resident in the spongelets, and the latter in 

 the cortical pores. It is worthy of remark, as connected with this question, 

 that coloured fluids, which find an easy ingress through the spongelets, will 

 not pass through the cortical orifices. The superfluous egesta occasioned by 

 an unusual richness of the soil cannot be evolved in a sufficient ratio by the 

 foliage. During the presence of the sunbeams, leaves cast off oxygen, while 

 the carbon of the carbonic acid gas is appropriated and assimilated : but it is 

 by no means probable that the entire quantity of carbonic acid gas which rises 

 in the stem during the day can be constantly decomposed amid the various 

 changes of light and shade, to make no mention of the liquid matter which 

 has been evolved." 



In treating of the blossom (chap, v.), the author adverts to it as the found- 

 ation of the beautiful system of Linnaeus, upon which he passes the highest 

 eulogium, while he asserts that "what has been lauded as the natural system is 

 the most unnatural jumble of incongruities that ever was collected together." 



We shall next give a few extracts from an interesting part of the chapter, 

 where it is demonstrated by experiments " that, in the sunbeam, each indivi- 

 dual colour of the chromatic series, as arranged upon the painted disc of the 

 flower, denotes the evolution of a peculiar grade of temperature, in exact 

 unison with that evolved in the same tints of the prism. The late Sir W. 

 Herschel found that a delicate thermometer, placed in the violet ray of the 

 solar spectrum, indicated an acquired temperature of 2° above the ambient 

 atmosphere. The green exhibited an increase of 2-25°, and the maximum 

 of temperature in the red ray amounted to 4*5833 Fahr." In verification of 

 these facts, the author refers to experiments by which he discovered, from the 

 degree of caloric that followed the formation of a peculiar colour, produced 

 by the chemical union of different substances, " that each colour of the pris- 

 matic series displays, at the instant of its evolution, a corresponding and 

 peculiar temperature. The results yielded, for violet, 1°; blue, l'5°j yellow, 



