220 



Keegan : The Wild Cherry. 



living- tissues. A feverish activity of division, etc., leads to 

 a preliminary disorganisation of the protoplasm of those special 

 cells wherein it occurs. The consequence is an abnormal forma- 

 tion of powerful ferments, which break down and disorganise 

 the pectic substances and the celluloses in their vicinity. In 

 fact, in this tree the process is so powerful and so complete that 

 no trace of cellulose is left as a residuum in the gum itself, and 

 the inclination to form arabinose groups therein is much stronger 

 than that to form galactose groups. 



Leaves.— The mesophyll is composed of one layer of palisade 

 cells about four times as long as broad, and a rather loose 

 lacunar tissue irregularly disposed ; the lower epidermis has 

 about 240 stomata per square millimetre. This structure indi- 

 cates only medium capabilities of assimilation and transpiration, 

 and the leaf being thin it absorbs and transmits much heat. On 

 10th September the relation o? "absorbed was found to be = 0*92, 

 showing only a moderate amount of oxidation. Chlorophyll has 

 been observed in the young spring leaf before any visible starch 

 appeared ; but the production of the latter seems well sustained 

 throughout the life of the organ. Carotin is abundant, and so 

 is wax, but there is very little fat-oil. The nitrogenous sub- 

 stances in the fresh leaf vary from about 12*5 per cent, in April 

 to about o"7 per cent, in October. A copious abundance of 

 glucose or maltose is detectable at times in the conducting 

 tissues of the nerves, while a plate of gum covers the lower wall 

 of the cells of the upper epidermis ; oxalate of calcium is very 

 prevalent from an early age. Much rutin is found in the young 

 leaves, and, as the season advances, tannin is formed to the 

 amount of about 10 per cent, in autumn. A very remarkable 

 feature of the organ is that the proportion of mineral matters 

 therein, i.e., in the dry leaf, practically remains the same, viz.., 

 about 7 '5 per cent, from April till October. The ash (reckoning 

 from spring- till autumn) contains 30 to 44 per cent, lime, 7 to 17 

 magnesia, 32 to 11 potash, 4 to 13 oxide of manganese, and only 

 1 '4 to 2*3 silica. Roundish or reniform fleshy glands are deve- 

 loped on the leaf stalk at the base of the blade and sometimes on 

 the serratures of the blade itself, and freely secrete globules of a 

 transparent thin liquor, which ultimately runs together into a 

 sheet or drop ; the maximum volume of this nectar (which 

 consists of a solution of cane-sugar and glucose in varying 

 proportions) always takes place before the leaves attain their full 

 development, and, in proportion as they become completely 

 developed, the emission diminishes and then ceases. 



Naturalist, 



