IN FALLING LEAVES. 229 



and Poplar the form and colour of these minute bodies melt away 

 together, after the earlier disappearance of the starch. In the 

 Horse chestnut all seem to go about the same time. The main 

 point to be observed is that there is a definite emptying by means 

 of colliquative changes in the Chlorophyll bodies. And it is to 

 these changes, with their results, that the well-known hues and 

 tints of autumn are due. Thus (i.) in place of the real green 

 and definite form of the Chlorophyll corpuscle there are found in 

 autumn leaves, before they fall, numbers of yellow oil drops, with 

 still larger quantities of very small yellow granules. Their colour 

 and substance are quite distinct from the Etiolin which precedes 

 the appearance of Chlorophyll. They are, moreover, often 

 embedded in red sap, whence arises the beautiful colouring which 

 some leaves exhibit, (ii.) The means by which this economic 

 work is done will be easily apprehended by all who bear in mind 

 what is known as the Fibro-Vascular System. This is far too 

 complicated to admit of detailed description here. Any good 

 book upon Botany, moreover, (e.g., Prantl and Vines) will supply 

 the requisite information. Perhaps the best possible illustration 

 of this system is found in those specimens of the " veins " of 

 leaves, which are often obtained by maceration of the softer 

 parts. These so-called veins, when examined microscopically, 

 exhibit a series of tubes and vessels, the function of which is 

 exceedingly difficult to define in detail, but which amply suffice to 

 afford channels whereby food materials may be transported. It is 

 not needful, therefore, to step aside here and decide the mixed 

 puzzles of Histology and Biology. That (iii.) the emptying process 

 referred to does take place, can be shown to conviction in 

 several ways. First, by micro-chemical testing, w^hich shows that 

 in the just fallen leaf there is scarcely a trace of starch, whereas the 

 vigorous leaf abounds with it. Or, again, it may be demonstrated 

 by testing carefully the chemical constituents of the ash of a leaf 

 in full vigour, as compared with that of one naturally fallen. The 

 presence in the former, and absence in the latter, of potash and 

 phosphates is manifest and sufficient. 



(3) The drained leaf-skeletons being then, obviously, of no 

 service to the parent organism during the following six months, it 

 is highly desirable that such should be removed. And in con- 



