THE LEAF AS A PHYSICAL STUDY. 135 



The beautiful green of the leaf, so restful to the e^'e, is a waxy 

 substance termed chlorophyl {chloros, green, and pliyUnn^ a leaf). 

 It is soluble in chloroform and ether, but insoluble in water, and 

 floats in the fluid of the cells as minute granules. The liglit of the 

 sun seems to be essential to its formation. Although found in 

 vast abundance in the vegetable kingdom, hundreds of tons being 

 everywhere about us, chemists can tell, or have told us, but very 

 little about it. The}' have not yet ascertained its component 

 elements, much less their relative proportions. They cannot tell 

 whether it contains iron or nitrogen ; they have only got so far 

 that they can sa}' it is never produced in ^he absence of com- 

 pounds capable of supplying those elements. It is possible that 

 it ma}- contain more than one substance, or that the leaf green of 

 all plants is not in every respect identical. Chlorophyl is found in 

 those cells of plants where the absorption and decomposition of 

 carbonic acid gas go on ; with which characteristic process of 

 vegetable life it is closely connected. Thus starch granules are 

 formed in the midst of a complex material, to which the name of 

 protoplasm is given, this formative material being dyed as it were 

 with chlorophyl. It is then extremely probable that chlorophyl, 

 under the sun's radiant energy, stands, in relation to carbonic 

 acid gas which is decomposed by plants, in very much the same 

 position of importance that htemaglobin does to the gas of our 

 own blood; showing that the principle called "life" in the 

 vegetable kingdom is similar to that in the animal. Solutions of 

 chlorophyl present a very fickle color when viewed in different 

 positions, being either bright green, opaque red, or vermilion. 



A second coloring matter is also found, common alike to fruits 

 and flowers ; as in the leaves of the red cabbage, the skin of the 

 grape, and in that majestic queen of the garden, thedalilia. It has 

 passed at different times under various names ; but now I believe 

 colein is the term most generally accepted, from coleus, a genus of 

 plants in many species of which it occurs abundantly. It is 

 generally very irregular in distribution ; and might be called one of 

 the curiosities of the leaf, as it has no important office to fulfil. 

 The chemist is full of information regarding this principle, and 

 gives as its percentage composition, — carbon, 57.7 ; hydrogen, 4.7 ; 

 oxygen, 37.6 ; making it identical with the coloiing matter of red 

 wine and most red, blue, and pur|)le flowers and fruits, and with the 

 red pigment of some of the varieties of the beech ; for with am- 

 monia it becomes violet, indigo, green, and yellow. May we not 



