Leaf—The microscopic structure and the chem ical composition of the leaves determine the amount of resistance they will offer to the attacks of the various fungi that are peculiar to this part of the plant. This subject is one that has not yet been sufficiently studied to determine the precise nature of the various factors, but it is known to growers that certain varieties are more susceptible to leaf diseases than others. For example, the yellow varieties are more susceptible to many leaf diseases than the red and green varieties. It is now known that the various structures indicated vary to a considerable extent in the different varieties, and it is reasonable to suppose that some of these vari ations are correlated to resistance to disease. The thickness and the chemical composition of the cell walls will determine the resistance of the internal cells to the dissolving effect of parasitic fungi. So, too, the thickness of the cuticle and its chemical composition will determine the resistance to such fungi as dissolve their way through the cuticle. No doubt many of the fungi that enter the cane-leaf do so by way of the stomata. It is known that these vary in number and structure in the various varie ties and thus offer various degrees of ease with which the parasites may enter. Again, it is through the stomata that a number of these parasites make their exit for fructification. Here, again, the num ber and size of the openings determine the degree of resistance to the formation of fructifications.
Resistance to drought is largely a function of the leaves, for it is through the opening and closing of the stomatic openings that transpiration is con trolled. A variety that promptly and effectually closes its stomata under dry conditions is one that, other things being equal, resists drought best.
At certain periods of its growth, it is customary in some localities to strip the stalk of its lower leaves in order to facilitate the ripening processes. The attachment of the leaf is a factor of impor tance in this connection. In some varieties the leaf comes away with ease, and leaves a beneficent scar, while in other varieties when the leaf is removed the connection is such that there is a tendency to tear away some of the tissue of the stalk, and thus leave wounds which may be entered by wound parasites that work injury to the cane in reducing the sucrose. The attachment of the leaves is also related to disease in another way. In some varieties the sheath of the leaf is so related to the stalk as to resist the entrance of both insect and fungous parasites, while other varieties admit of the early entrance of mois ture and injurious parasites.
It is the large leaved varieties that, as a rule, are the most pro lific, although, un fortunately, also generally the most subject to disease. It ap pears that the rapid growth re sulting in the pro duction of large leaves is more or less incompatible with the produc tion of disease resistant tissues.
Flower.—Of re cent years, t h e structure of the flower of the cane plant has assumed great importance because of the at tempts to produce new canes by crossing known varieties. These attempts and the resulting studies have disclosed a number of very interesting facts with regard to the anatomy and physiology of the blossom. Until recent years it was thought that the blossoms of the cane plant were infertile and that such a thing as a cane seedling was an impossibility. In the latter eighties, however, seedling canes were reared, and from that time much progress has been made in the art of producing new varieties. In the following countries and in the following order, approximately, the subject has received attention: Java, Australia, West Indies, Hawaii. The making of definite crosses was first successful, it is thought, in the West Indies. The greatest amount of this work has thus far been accomplished in the West Indies, although it has now begun in Hawaii and elsewhere. The following facts have been slowly developed : The number of fertile seeds produced in a panicle of cane is relatively small, as is the case with many other grasses. The germinating power is very transient, being at a maximum a few days after ripening and rapidly decreasing thereafter so that at the end of a few weeks it is often wholly lost. An examination of the seeds of cane discloses the fact that a large proportion of them are shrunken, and this seems to indicate that a large proportion of them are not fertilized. Nearly all the plump seeds germinate when they are a few days old if they are soaked in water for 12 hours and placed in a saturated air of 100° Fahr. These are probably the properly fertilized seeds. It is rare for certain vari eties to produce fertile seed ; in fact, a large num ber of varieties are not yet known to produce them, though this may be due to insufficient observa tion. On the other hand, it has been established by observation that the pollen of certain varieties is incapable of germination and therefore of prop erly fertilizing the ovaries. This fact is deter mined by the structure of the pollen, and by the fact that it will fail to develop when given the proper conditions. In some instances the anthers appear never to ripen properly, as they are thin, off color, and never open at all. On other occasions they appear to contain pollen mother-cells only, the growth appearing to be arrested at that stage. Attempts to secure fertile seed with such anthers end in failure. It is possible that the method of propagating cane solely by means of cuttings has ended in a deterioration of the seed -producing powers, and that perseverance in the effort to secure successive generations of seedlings may resuscitate this power. It is to be hoped that this is the case, as it is some of the very best varieties that have apparently failed hitherto to produce good seed.