390 Journal of Agricultural Research \u\. iii. no. s 



DIFFERENT DEGREES OF BRACHYSM 



The interest of brachytic variations as a phenomenon of heredity is 

 increased by the fact that the tendency is manifested in many different 

 degrees. The most extreme form of brachysra is represented b\' a com- 

 plete abortion of the fruiting branches, but there is an apparently com- 

 plete series of stages from these completely sterile monstrosities to the 

 normal long-jointed forms. The strictly cluster or limbless forms have 

 the fruiting branches reduced to a single joint or a few very short joints, 

 as shown in Plate LVI. From this extreme condition the intermediate 

 stages run through the ordinary cluster and semicluster types to those 

 that show no reduction of the joints of the fruiting branches. Even in 

 the same field of cotton it is often possible to find a wide range of varia- 

 tions in the lengths of the internodes of the fruiting branches, especiallv 

 in varieties like the King, that produce many brachytic variations. 



In some varieties, such as the Triumph cotton of Texas, the lower 

 fruiting branches often show a tendency to brachysm not shared by 

 branches farther up. Other varieties show the opposite tendency to form 

 long-jointed fruiting branches on the lower part of the stalk and short- 

 jointed branches on the upper part. Some varieties that usually have 

 long-jointed fruiting branches show the cluster tendency when the 

 growth of the plants is restricted by unfavorable conditions, while other 

 varieties are always short-jointed. There may also be pronounced irregu- 

 larities in the lengths of the joints, even on the same fruiting branch. 

 (See Pis. L\1I and LVHI.) 



In addition to the fundamental difference between the vegetative and 

 fruiting branches, the basal intemode of the fruiting branches is generally 

 longer than the others and often maintains its length when the others 

 are shortened. In a peculiar variety of Egyptian cotton grown in experi- 

 mental plantings at Bard, Cal., under the name of Dale, most of the 

 fruiting branches develop only this long basal intemode, and produce 

 only a single boll, the other internodes being aborted. (See PI. LXII.) 

 When the leaves, buds, and joints of such branches are suppressed, the boll 

 appears to be borne on a greatly elongated pedicel. 



The extent to which these abnormalities are often carried may be more 

 easily understood by reference to the photographs of the plant shown in 

 Plate LXI, figure i. The main stalk was rendered completely sterile 

 by the abortion of all of the fruiting branches, though the vegetative 

 branches of the same plant produced a few fruiting branches and ripened 

 a few bolls. Finally the growth of the main stalk was stopped by the 

 abortion of the terminal bud. (See PI. LXI, fig. 2.) In more normal 

 plants of this variety the single- jointed fruiting branches are often accom- 

 panied by one or two other branches of similar form arising from the 

 axillary bud. (See PI. LXII.) In an extreme case like that shown in 

 Plate LXI, the axillary huds abort, as well as the extra-axillarv buds 



