THE CANE 5 



or pale green, and about 12 inches long at maturity. The blade is from 

 3 to 4 feet long, and 2 to 3 inches wide ; in colour the leaves are varying 

 shades of green ; in some varieties variegated or entirely white leaves are 

 often developed. Some canes (S. violaceum) have purple leaves. The leaves 

 taper towards the top, and are delicately serrated along the margin ; in 

 many varieties seta or hairs abound at their base. The leaf is traversed 

 longitudinally by a number of veins. The midrib is generally white, but 

 sometimes reddish or purple, and is formed with a channel-like depression 

 in its upper surface. Leaves at maturity fall away from the stalk, and in 

 some varieties separate themselves entirely. 



Structure of the Leaf. In Fig. 4 is shown a cross section of a leaf of the 

 cane, to which must be added Dr. Cobb's explanation of the plate. 2 



30 21 



FIG. 4 



" Cross-section of a portion of healthy cane leaf taken half-way between the 

 midrib and the margin near the middle of a full-grown but not yet fully Hgnified 

 leaf. The upper side of the figure, I to 18, represents the top surface of the leaf. 

 The fructifications of the leaf -splitting disease occur in positions corresponding to 

 3, 4, 5. The green chlorophyll bodies are here shown black. It is owing to the 

 destruction of these green bodies in portions of the leaf such as here represented, 

 namely, between the largest vascular bundles, that the leaf takes on a striped 

 appearance. The part of the leaf to be examined was fixed with the vapour of 

 osmic acid while still attached to the cane plant. The fixed portion was differenti- 

 ated into glycerine and cut in that condition. The drawing was projected from a 

 photograph and sketched. The details were drawn in from the examination of 

 sections either unstained or stained with aniline safranin. The section shows five 

 fibro- vascular bundles, the largest of which is indicated at 6 to n, the smallest 

 at 23 and 32. Portions of the other two, which are intermediate in size, are shown 

 at 19 and 36. None of these bundles are of the largest size. Bundles fully twice 

 the size of the larger here shown occur in the cane leaf, and such large bundles are 

 characterized by the possession of annular vessels, none of which occur in these 

 smaller bundles. Throughout the illustration structures of the same class are 

 indicated b}' a similarity in the draughtsmanship ; thus the woody cells indicated 



