KNOWIJ.DC.I.. 

 Double Stars.— The limits of K.A. art- 1 1" to l j" 



Maucii. 1<)12. 



THE TINTS AND SHADES OF AUTUMN WOODS. 



By P. g. KKHCxAN. LL.D. 



iContiiiiicd from pcific 51 



What then is the specific cause of the aiituniiial 

 red colouration of the forest leaf? It is undouhtcdl\- 

 produced siinilarly to that of the red petal (see 

 January nimiber of this journal, page 15), the 

 albuminoid molecule is disrupted, but not because 

 there is a violent demand for its nitrogen aiul 

 phosphorous elsewhere {i.e.. in the pistil), as in the 

 case of the floral organ. No, the disruption of 

 autumn ensues because the cell plasm gradually 

 loses its vitality- ; nitrogen becomes deficient, but it is 

 not draw n away, nor is it reproduced /;; loco ; there 

 is a difl'erent chemism because there is a change of 

 nature of the plasm, and so long as it still lives it 

 can do with less nitrogen, the nitrogenous content 

 of forest litter being in all these special cases com- 

 paratively small. Moreover, behold also a most 

 interesting difference ! The physiological processes 

 going on in stamens and pistils in connection with 

 fecundation and reproduction are so vigorous and 

 powerful that special and peculiar tannoid chromo- 

 gens are produced in the petals, which frequently 

 evolve extremely vivid and brilliant pigments. Hut 

 this is not the case with the fading glories of 

 the woodlands. The autumn leaf is far too feeble 

 and exhausted to permit of any such demonstration 

 of energy. The tannoid of its early life is gradually. 



as tlio suinniir months elapse, converted into 

 tannin, which, moreover, may have a different 

 chemical composition and constitution from that 

 which the flower of the same plant evolves, or 

 nia\' e\-ol\e. Thus, in the petals of Foxglove. 

 and so on, tannoids arc found which are utterly 

 absent in an\' of the otlu-r organs at any period 

 of their existence. 



On the other hand, where, as in the yellow, 

 brown, and russet lea\"es, the albuminoid becomes 

 insoluble and passive and remains permanently 

 stored up, as it were, there is no special deassimila- 

 tion thereof ; its chemical transformation has ceased, 

 and hence there is no fresh production of tannin and 

 pigment. Hence the brown shades may be regarded 

 as a mere decomposition product, dull and dead, 

 which ultimately impregnates the dry coagulated 

 cell-contents massed against the equally lifeless cell- 

 wall. We have already seen how this phenomenon 

 coincides w ith a high percentage of total ash con- 

 taining a very high percentage of silica : which means 

 that the inert physiological condition has permitted 

 the encroachment of all this encrusting matter more 

 especially upon the epidermal cells, the ver\- spot 

 where under other conditions the brilliant autumn 

 tints are specially evolved. 



