124 TILLERING IN INDIAN SUGARCANeS 



(6) Average thickness of branches of different orders. 



As we pass from the main shoots to branches of higher orders, we note, 

 in the dissections, a steady increase in the thickness of the canes. This is 

 not to be wondered at, if we regard each shoot as being furnished with a certain 

 amount of energy of growth. Much of this energy is used up in the main 

 shoot in its change from the infinitesimal stem of the young seedling to a cane 

 of definite thickness. The branches, on the other hand, not only are thicker 

 at the start, but pass through their forming process much more rapidly, and 

 it is to be expected that, before their energy wanes, stronger, thicker canes will 

 be produced. 



To compare the thickness of the canes, all have been measured in each 

 plant at about 2' from the base, where it is reasonable to suppose that the 

 cane has completed its growth in thickness. The measurements were made by 

 calipers in the lateral plane, thus ruling out the ovalness of some varieties, 

 the longer diameter usually occurring in the median plane or that in Avhich 

 the buds lie. The markings on the calipers are in mm., and the results are 

 accordingly given in the metric system. The following are the average thick- 

 nesses, in mm., of the main stem and its branches of difi'erent degree, in all the 

 groups dissected, a 177, b 187, c 207, d 228, e 219, / 88. The last two figures 

 are not true averages, / only occurring in the thinnest form, namely, SaccJiarum 

 spontaneum, and e being absent in the Thick canes, Sunnabile, Nargori, 

 Unclassified indigenous and Crosses, in all of which groups the branches which are 

 present show markedly rapid increases. As in the case of the average length 

 of joints, there is a distinct advance from a to b, but there is a much greater 

 one from b to c. In the main groups of indigenous Indian canes, there is less 

 difEerence between the «s and 6s. This, as has been noted elsewhere, may be 

 put down to several causes. In the first place, both are formed at a very 

 early stage of the plant's growth — ^before the general elongating stage has been 

 reached — ^the plant is small and thin and has comparatively few roots and 

 leaves. In the second place, cases are not infrequently met with in which, an 

 having died, one or more of the 6s become facultative os, and the energies of 

 these are devoted rather to branching than to increase in thickness. Thirdly, 

 there are more 6s on an a than cs on a 6, and, as we have seen, this leads to a 

 tailing oil of the later-formed 6s, when the energy of the main shoot is waning 

 (c/. p. 107). Lastly, other irregularities occur owing to the deaths of as and 

 the consequent relative numbers of as and 6s in a plant. Thus, in Kharwi, 

 the thinnest of the Mimgo group, 3 as and 19 68 were measured, whereas in 

 Hemja, the thickest cane in the group, there are 15 «s and 27 6s. In taking 



