24 DIMORPHIC BRANCHES IN TROPICAL CROP PLANTS. 



In extreme cases a single long-stemmed boll may arise from the 

 axil of a leaf at the base of the fertile branch. This might be taken 

 to indicate a direct transformation of the axillary bud into a fertile 

 branch ; but further examination will usually show, even on the same 

 plant, great variation in the pedicels of these axillary bolls, making 

 it evident that they are not simple pedicels, but shortened branches. 

 Small bractlike leaves or stipules are occasionally present, even on 

 straight stems, and sometimes the joint between the branch proper 

 and the true stem or pedicel of the boll remains distinct, even when 

 there are no leaves or stipules. (See PI. II.) 



Where the axillary branches are longer and more definitely jointed 

 it becomes possible to see that the bolls are really borne on a short 

 fertile branch that rises in turn from a short true axillary branch, 

 instead of being inserted directly on the main stem. A shortened 

 axillary branch may represent three normally independent elements, 

 an axillary vegetative branch, a secondary fertile branch borne on 

 the axillary, and the pedicel of the boll, all fused into a simple stem. 

 In some cases it is plain that the true axillary branch has remained 

 entirely undeveloped, for an axillary bud or bud scar can often be 

 found at the base of one of the shortened branches. When no such 

 mark is found it may be supposed that the axillary bud was carried 

 out by the growing branch. It is seldom necessary to suppose that 

 the axillary bud is directly transformed into a flower bud, since the 

 existing conditions can also be reached by fusing tlie successive joints 

 together, much as they are fused in the formation of a normal in- 

 volucre. 



The idea of translocation may be applied to these abnormalities of 

 the Egyptian cotton, or it may be combined with the idea of hybridi- 

 zation, in view of the many intermediate stages between the parts that 

 are nonnally quite unlike. The fact that sterility so generally ac- 

 companies these intermediate conditions is a further reason for look- 

 ing upon translocation as a phenomenon akin to hybridization. 

 Changes that might be looked upon as results of partial transloca- 

 tions of characters might also be considered as hybrid metamers or 

 metameric hybrids. They represent abnormal intermediate stages 

 between metamers that are quite unlike when normally developed. 

 They indicate an abnormal intermediate expression of the charac- 

 ters rather than an abnormal transmission of characters to new parts 

 of the plant. All of the hereditaiy characters are probably trans- 

 mitted to all parts of the plant, since all of the internodes are able, 

 directly or indirectly, to produce flowers and seeds, but the growth 

 of the normal plant involves the full expression of each character 

 in the appropriate place and its complete suppression in other parts 

 of the plant. Failure of the proper suppression of a character 



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