134 STUDIES IN INDIAN COTTONS 



In the pure types the dift'erence between the two groups in 

 which the secondary branches are monopodial and syinpodial res- 

 pectively is readily distinguished. In the monopodial types even 

 the ultimate secondary branches are monopodial. In the syinpo- 

 dial types, however, although single plants are to be found in which 

 no monopodial secondary branches occur, in general a few of the 

 lowest of these branches are monopodial. Thus m Plate VI a 

 single short monopodial branch is developed, and, similarly, one 

 such branch only occurs in Plate IX. Plate VIII demonstrates the 

 maximum development of monopodial branching found in the 

 syinpodial types but, even here, the type is quite distinct from the 

 monopodial type illustrated in Plate III. When, however, the 

 progeny of crosses between types belonging to these two groups is 

 considered, every gradation between the two extreme forms is 

 found. In as much as, however, the change from monopodial 

 to sympodial secondary branching is abrupt, the main stem 

 is divisible into two portions, a lower bearing monopodia and 

 an upper bearing sympodia, and this character can be con- 

 veniently expressed as the percentage of the stem bearing 

 monopodial branches. Thus 100 will represent, in this ter- 

 minology, the full monopodial type and the full sympodial 

 type which, however, includes the forms with a few basal monopodia 

 such as are found in pure types. Plate XVIII illustrates an inter- 

 mediate type represented by the symbol 70. It is clear that this 

 determination can only be made at the end of the growing period 

 and also that, to obtain such a symbol in any particular case, the 

 main axis of the plant must continue to grow. Unfortunately, in 

 practice, this occurs in comparatively few cases. Through various 

 natural coiKlitions, and especially owing to the attacks of larvae of 

 Earias .sp., which penetrate the leaf axil of the young cotton plant 

 and bore their way down the stem, the main axis is frequently 

 destroyed and growth carried on by lateral branches. In such 

 cases, this determination is not possible, and it is necessary to resort 

 to some other method for determming the character of the plant. 

 Such is to be found in direct measurement of the length of the vege- 

 tative period. 



