232 Studies in Indian Cotton 



is limited to pure types these two groups are readily distinguished. 

 When, however, the progeny of crosses between types belonging to 

 these two groups come to be considered, every gradation between the 

 two extreme forms is found and it becomes a matter of extreme 

 difficulty in individual cases to define the degree of approximation to 

 one or the other extreme type. In such intermediate plants the 

 passage from one type of secondary branching to the other is usually 

 abrupt, the earlier branches being monopodia and the later sympodia. 

 It is, therefore, possible to divide the main stem into two portions, 

 a lower portion in which the branches are monopodia and an upper 

 portion in which the branches are sympodia. The character can then 

 be conveniently expressed as the percentage of the entire stem bearing 

 monopodial branches. Expressed in these terms a pure monopodial 

 type is indicated by the number 100 and a pure sympodial type by 

 the number 0. It has already been stated that no pure type has been 

 isolated which invariably produces sympodial secondary branches only. 

 A few monopodial branches may in all cases occur at the base of the 

 primary stem. It is convenient, therefore, to denote these also by the 

 symbol which indicates all such sympodial types as have been found 

 to breed true. In like manner the symbol 100 may be used to denote 

 cases in which a few of the most apical branches are sympodial. In 

 the earlier experimental stages it was considered sufficient to recognise 

 four divisions only : 



(1) The full monopodial type indicated by 100. 



(2) Approximately three-quarters of the secondary branches mono- 

 podial, indicated by the symbol 75. 



(3) Approximately one-half of the secondary branches monopodiah 

 indicated by the symbol 50. 



(4) The sympodial type indicated by the symbol 0. Recently the 

 separate forms have been recorded in greater detail by which the 

 fraction, recorded in tenths, of the main stem bearing monopodial 

 secondary branches is used as a basis for division. By this method 

 10 groups are formed, the relation of which to the four groups given 

 above is shown below. 



100 90 80 70 60 50 40 30 20 10 



In this notation the figures 100 and apply respectively only to 



individuals in which sympodial and monopodial secondary branches 

 are entirely absent. 



