AUGUST. 391 



flowers, for which a reason and a purpose are not so easily 

 assigned. Tlie purpose served by the greenness of the foliage 

 of all or nearly all plants may not be a single one. It seems 

 to me not improbable that nature has selected it as a ground- 

 work upon which the flowers are rendered more conspicuous 

 than they could be rendered by any other color. Of this fact 

 the makers of bouquets are fully aware. A few flowers, 

 placed on a background of green foliage, make a better show 

 than a whole bunch of the brightest flowers without any such 

 opposition. No other color can be selected that could so well 

 answer this purpose. Nature, for this reason, has selected it 

 to render the flowers, by opposition, more discernible by the 

 insects, whose agency is required in their fertilization. 



The primary object of nature, however, in giving this hue 

 to the foliage of vegetation, is probably the adaptedness of a 

 green color to promote that degree and kind of absorption of 

 light which is necessary for the oxygenating process, carried 

 on by the leaves or the lungs of the plant. Our knowledge 

 of vital chemistry is not yet sufficient to enable us to assign 

 the peculiar action of the green color of the leaf upon th6^ 

 juices of the vegetable. Green is probably that medium tint 

 which is most favorable to the moderate action of the sun's 

 rays, which would be too powerful as generators of heat in a 

 darker colored leaf, or as generators of oxygen in the lighter 

 colored one. 



dltiurnl flctins. 



Effect of Frost on Vegetation. — The long and excellent report 

 upon the effect of the last winter upon the vegetation near Dublin, which 

 we have lately published, led to some discussion, for which we have not be- 

 fore found room. The question raised was, in what manner does cold act 

 upon plants when it causes death ? 



Dr. Steele expressed his opinion that this was not properly understood. 

 To the theory that death ensued from a too great distention of their tissues, 

 caused by the congelation of their fluids, he objected. On the contrary, he 

 thought that the action was in some way similar to that caused by an elec- 

 tric shock on succulent plants, such as the garden balsam. That a disten- 



