CANE SUGAR. 



The sieve tubes seen in longitudinal section are observed to be very 

 elongated cells, with perforated partition walls at intervals in their length J 

 the vessels are continuous throughout their length. 



In the internodes the fibro- vascular bundles run parallel, but at the nodes 

 they freely branch and communicate with each other, and pass on into the leaf 

 and into the next internode, passing down right into the roots of the cane. 



The physiological function of the nbro-vascular bundles, apart from their 

 mechanical action, is to transmit water, charged with food material, from the 

 root to the leaf of the cane ; this water passes upwards by way of the vessels 

 to the leaf, where it is elaborated, and then passes downwards through the sieve 

 tubes to be either stored in the parenchymatous cells or to be used up in the 

 economy of the growing plant ; the function of the companion cells is not 

 thoroughly understood. 



Structure of the Leaf. In Fig. 5 is shown a cross section of a 

 leaf of the cane, to which we add Dr. Cobb's explanation of the plate. 



" 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 lignified 

 leaf. The upper side of the figure, 1 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 differentiated 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 11, 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 by a similarity 

 in the draughtsmanship, thus the woody cells indicated at 9 are repeated in various 

 parts of the figure, more particularly next to the epidermis of the lower surface. 



" 1, a set of so-called motor cells, in this instance composed of two cells, whose 

 nuclei are pointed out at 2 and 3 ; 4, an internal cell of somewhat similar character 

 to that pointed out at 1,2, and 3 ; 5, another cell of the same class cut in such a 

 way that the nucleus has been removed ; 6, sclerenchyinatous cells imparting 

 strength to the fibro-vascular bundle ; 7, one of the layer of parenchymatous cells 

 rich in chloroplasts and immediately surrounding each fibro-vascular bundle ; 8, one 

 of the stomata, found more rarely on the upper than on the lower surface of the 

 leaf; 9, woody cells imparting strength to the cane leaf, and occurring on the dorsal 

 and ventral side of each fibro-vascular bundle ; 10, one of the cells constituting the 

 sheath of the vascular bundle, these cells contain chloroplasts arranged along the 

 outsides of their walls; 11, tracheal vessel; 12, one of the cells of the upper 

 epidermis; 13, nucleus of a similar cell; 14, upper cuticle at its usual thickness; 

 15, a two-celled hair on the surface of the leaf ; 16, thinner cuticle of the upper 

 surface of the leaf as it occurs over the so-called motor cells; 17-18, group of 

 so-called motor cells, consisting in this case of four cells ; 19, fibro-vascular bundle 



