326 



The Journal of Heredity 



prominent than in China, the marginal 

 areas being chiefly affected and those 

 that are intermediate between the prin- 

 cipal veins. The marginal and inter- 

 mediate areas show a paler green at 

 first, then become red, and finally turn 

 brownish and die. 



Some of the mosaic diseases have 

 been traced to bites of insects, which are 

 supposed to convey organic infections 

 or protoplasmic poisons that are able 

 to extend like enzymes through the 

 whole system of the plant, though the 

 injuries become apparent only in the 

 new growth of the plants, which is dis- 

 colored and distorted. The change 

 from the normal to the abnormal 

 growth appears very abrupt. The leaf 

 that subtends a fruiting branch may be 

 quite normal, while the first leaf of the 

 fruiting branch is definitely affected. 

 The effects of the injury are the same 

 in the different parts of the plant, the 

 same abnormal characters appearing at 

 the top of the plant and at the ends of 

 all of the growing branches. 



Whether unknown parasitic organ- 

 isms are involved in such diseases, or 

 injurious chemical compounds acting 

 like ferments or enzymes, the effects 

 upon the development of the plants are 

 of much interest from the standpoint 

 of heredity. The aberrant growth of 

 the plants shows very clearly that the 

 normal course of development, as de- 

 termined by heredity and manifested in 

 the normal early growth of the plants, 

 is subject to serious and persistent de- 

 rangements through some cause or 

 causes that are still unknown. The in- 

 vestigation of such abnormalities may 

 throw light on problems of heredity, 

 in addition to the purpose of avoiding 

 losses of crops. 



The Upland type of cotton in Haiti 

 showed a more general distortion and 

 buckling of the leaves, with less ten- 

 dency to discoloration and rolling-under 

 of the leaf-margins, which were the 

 special symptoms with Upland cotton 

 in China. On badly affected plants in 

 Haiti where the leaves were dying, they 

 turned red along the margins and be- 

 tween the veins, though these symptoms 



did not appear with such regularity as 

 in China. In severe cases, the redden- 

 ing goes in between the veins, the 

 tissue dies, and the margins become 

 ragged, or the leaves may become quite 

 deeply dissected as the tissue dies back 

 between the veins. 



The behavior of Upland cotton in 

 Haiti is more like that of the Asiatic 

 type of cotton in China, except that the 

 growth of distorted leaves did not form 

 such dense, club-shaped masses as in 

 the Chinese cotton. The dense masses 

 of foliage in the Chinese cotton result- 

 ed from shortening the internodes and 

 increasing the number of branches, 

 which also are features of the Haitian 

 disease, but not to the same extent. On 

 the other hand, the tendency to reduce 

 the affected parts to very small size is 

 carried notably farther in Haiti than in 

 China. There were not in China such 

 extreme cases of reduction of leaves 

 and flower buds as shown in Figure Ki. 



The symptoms of the disease in 

 Haiti did not seem to be modified by 

 the conditions in the same way or to 

 the same extent as in China. Though 

 some plantings seemed to be more seri- 

 ously and more regularly deformed, 

 like the field planted to Lone Star, 

 cases of extreme deformity and dwarf- 

 ing also occurred among the normal, 

 uninjured plants. This is consistent 

 with the other fact of a wider range of 

 diversity in the nature and extent of 

 distortion and dwarfing of growth in 

 Haiti. As with the Chinese disease, the 

 Sea Island type of cotton showed less 

 dwarfing and distortion than the Up- 

 land type. One variety of Indian cot- 

 ton with very hairy leaves seemed to be 

 immune to the Chinese disease, while 

 the so-called "native" cotton in Haiti 

 seems not to be affected by the smalling 

 disease. 



Analogy of Gall Formation 



That there are substances which 

 have a specific action in changing the 

 course of normal development and pro- 

 ducing abnormal growth, is shown by 

 the familiar phenomena of gall-forma- 

 tion. Since the same plant may pro- 



