392 Journal of Agricultural Research voi. m. no. 5 



environmental shortening or false brachysm is often accompanied by 

 other abnormalities, like the inherited form of brachysm. On a short 

 intemode intercalated between two of normal length the pedicel is likely 

 to have a sloping or decurrent base, with the end of the intemode pro- 

 longed beyond the insertion of the pedicel, though usually not so much 

 as in cluster cottons. 



This irregularity is less difficult to understand when it is remembered 

 that the floral bud of each intemode develops in advance of the growth 

 of the next intemode. On account of this sequence of development, 

 two structural elements may be recognized in the intemodes, the tissues 

 that are developed early to support the pedicel and those that develop 

 somewhat later in connection with the next internode. If a change to 

 more favorable external conditions occurred during the growth of an 

 intemode, its effect must be greater upon the part of the intemode that 

 is the last to reach its full development. Thus, in connection with the 

 development of a longer internode next to a short one, a slight elongation 

 of the supporting part of the short internode would be induced, and a 

 resulting tension between the two sides of the intemode. This would 

 account for the tearing of the tissues at the base of the pedicel, which 

 often occurs. Hence, we see that a part of the abnormality of the inter- 

 nodes that accompanies brachysm may be capable of a simple mechanical 

 explanation, as arising from changes in external conditions during the 

 period of development of the affected intemodes. 



RETENTION OF BLASTED BUDS IN BRACHYTIC VARIETIES 



The facts of brachysm in cotton seem to indicate that the shortening 

 of the intemodes of the fruiting branches is in the nature of a premature 

 or accelerated expression of the floral character. This view seems 

 preferable to the idea that a new character has been substituted for an 

 old one in the mechanism of transmission, as usually assumed in theories 

 of mutation and MendeHsm, That the shortened intemodes partake of 

 the nature of the pedicels of the flowers is indicated not only by their 

 reduced length but by the fact that they are often completely fused with 

 the pedicels. At the base of a noraial pedicel is a joint or layer of spe- 

 cialized tissue indicated externally by the absence of hairs and oil glands 

 from the surface, but in cluster cottons the formation of this specialized 

 layer is irregular. It is one of the recognized peculiarities of cluster 

 cottons that abortive buds and those that are infested by boll-weevil 

 larvae often remain attached to the plant, whereas in varieties with nor- 

 mal fruiting branches the blasted buds are soon shed. The lack of definite 

 differentiation between the pedicels and the joints of the branches is 

 responsible for the more frequent retention of the buds in cluster varieties. 



Normal shedding of the buds takes place by the formation of a circular 

 fissure at the base of the pedicel, the subsequent wilting of the bud, and 



