200 



The Journal ot Heredity 



BLASTED BUD OF UPLAND COTTON 



Showing al)n()rmal attachiiient. This is a 

 short fruiting Ijranch with floral hud blasted, 

 but still attached by abnormal decurrent base 

 of pedicel. Slightly enlarged. (Fig. 3.) 



on the surface by a minute groove 

 ami In' aljsence of oil-glands from 

 a short ring of nodal tissue. Even 

 with the abnormal decurrent pedicel- 

 bases of the "cluster" cottons, abscis- 

 sion still follows the line of the socket, 

 along the stipular rim. (Sec Figures 

 3 and 4. ) The tearing apart of stipules, 

 as described and figured by Lloyd in a 

 brachytic \ariety, is itself an evidence 

 of the elongation (if the socket. Though 

 brach\sm is much less fre(|iienl in the 



Egyptian type of cotton than among 

 I'pland varieties, there is a more 

 distinct inequalit\- of the stipules on 

 the fruiting branches, the stipide that 

 is ne.xt to the floral but being l^roader 

 than the other, as though to provide 

 for the enlargement of the socket. (See 

 Figures 5 and 6.) Brae'h>sm has been 

 interpreted as a breaking down or 

 failure of the normal difTerentiation 

 between the fruiting branch internodes 

 anel the pedicel interoneles. Not only 

 are many of the joints imperfect where 

 the pedicels are inserted on the inter- 

 nodes, but the leaves and bracts of the 

 abnormal internodes and pedicels show- 

 abnormal, intermediate forms, the 

 Iciives more bract-like and the bracts 

 more leaf-like than on normal plants. 



RELATION TO GROWTH OF PLANTS 



With sockets of the normal, circular 

 or transversely elliptical form the 

 pedicels often begin to tear loose at the 

 base while the buds and their enclosing 

 involucres are still fresh and turgid. 

 The buds may wilt after being partially 

 detached, or may fall with scarcely any 

 wilting. That the sockets are too large 

 for the pedicel-bases becomes apparent 

 under a hand-lens, since a gap is formed 

 at once between the separating tissues 

 of the pedicel and the socket, indicating 

 a release of tension. This was noted 

 at San Antonio, Texas, under date of 

 July 21, 1913, and the observation has 

 been repeated on several occasions. 

 In such cases enlargement of the 

 sockets, rather than shrinkage of the 

 pedicels, would seem to be the 

 "mechanical stimulus" of sheddi5g. 

 Lloyd's studies of young bolls showed 

 retarded growth-rates, and led him 

 to the conclusion that "cessatir)n of 

 growth is one of the i)henomena of 

 abscission," though without recogniz- 

 ing the morphological relaiions. 



Checking the growth of the floral buels 

 or yoimg bolls while the vegetative 

 framework of the plant is developing 

 ra{)idly would explain why the s(x:kets 

 ma\- become too large for the {x-diex'ls. 

 Thegrowthof the fruitiug-branch inteT- 

 nodis must ct-nlinue, of course, in order 

 to support more internodes. buds and 



