I02 Keegan : The Sycamore. 



of rather wide cells is formed in the first year in the sub- 

 epidermal layer, and remains thin and living for a long time, 

 till finally plates of secondary periderm develop below it, and 

 ultimately produce a nearly smooth, hard, dry, chocolate- 

 coloured rhytidome, which eventually splits and peels off in 

 scales. The Sycamore is a starch-tree, i.e., while the starch 

 completely disappears from the bark in winter (mid-November 

 till 3rd March), that of the wood remains only slightly reduced 

 in quantity all the time. A piece of branch 2| inch in diameter, 

 felled in February, was examined : the dried bark had a small 

 quantity of white wax with traces of carotin and chlorophyll, 

 there was no resin apparently, the amount of tannin was under 

 I per cent., there was a little free phloroglucin, a little pectosic 

 mucilage, and free phlobaphene, a saponin-like glucoside, 

 some cane-sugar, about 10 per cent, oxalate of calcium, and 9.4 

 ash which had 6.6 per cent, soluble salts, 4.4 silica, 45.2 lime,, 

 with traces of magnesia, etc. ; the wood showed mere traces 

 of tannin and phloroglucin, and (air-dried) yielded about 0.5 

 per cent, of ash, which had 32.3 per cent, soluble salts, 4.4 

 silica, 21.5 lime, ^."j magnesia and manganese, 3.9 P^O^, and 

 3.9 SO^. It would seem that none of our ordinary well-known 

 timber or coppice trees yields a chemical analysis quite sO' 

 meagre as the foregoing. Even none of our sap-wood trees is 

 apparently so poverty-stricken as respects wax, resin, tannin, 

 etc. It is clear that the starch reserve of the Sycamore is 

 for a very long period in life utilized by the cambium for growth 

 in size, and for the evolution of new-shoots, but that it is easily 

 exhausted and spent in the prosecution of this work. Herewith 

 is connected the remarkable production of cane-sugar in the 

 bleeding sap of springtide — the increased tension (osmotic 

 pressure) thereof arising concurrently with the regeneration 

 of the starch in spring, but the outflow effect would be 

 comparatively insignificant if it were not for the remarkable 

 porosity of the vessels and their freedom from obstructive 

 accumulations of gum (xylan), resin, and tylose growths. 



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

 palisades, narrow, and occupying about half its thickness, and 

 a lacunar tissue of irregular cells with large air-spaces ; the cells 

 of the upper epidermis contain starch granules, and their inner 

 wall is slimed, the lower epidermis has on the surface a papillose 

 structure, and is coated with wax, the stomatic cells only bear- 

 ing starch, while simple one-celled hairs appear along the 



NatuLiKst, 



