268 



SCIENCE 



[N. S. Vol. XL VI. No. 1185 



with cotton, they have never seen this rust. 

 Many Mexican cotton growers on the Texas 

 border too make similar statements, while 

 one or two others insist that they have seen it 

 before. It seems therefore a puzzle how this 

 riist has escaped the general attention of 

 cotton growers. There is this point which 

 might be of value in considering the source of 

 the present outbreak. The Eio Grande valley 

 receives its irrigation water, not from the Eio 

 Grande, as is commonly supposed, but from 

 the San Juan river and other Mexican rivers. 

 The waters from these rivers empty in a basin 

 or valley in which cotton grows. It is there- 

 fore very probable that the waters of the San 

 Juan river have introduced weeds which act 

 as a host to the possible Puccinia stage of this 

 rust. It is also probable -that the waters of 

 these rivers have carried sporidia from Mexi- 

 can sources, which were now responsible for 

 the infection of the cotton ; all this however is 

 problematical. 



Cause. — The disease here reported is a true 

 rust. The ascial stage occurs on the cotton 

 while the Puccinia stage undoubtedly occurs on 

 some other host, unknown as yet. In submit- 

 ing specimens of this cotton rust to Dr. J. C. 

 Arthur, he pronounced it ^cidium gossypii 

 E. & E. suggesting also that this rust might 

 come from some grass form, probably Muhlen- 

 hergia, or Sporoholusj Dr. Arthur has spec- 

 imens of this rust in his herbarium, which was 

 collected by Heald and Wolf at Ealfurrias, 

 Texas, September 2, 1909, and two Mexican 

 collections, one from San Jose del Cabos, Sep- 

 tember 2, 1893, the other from Tlahualilo, 

 collected about 1907, probably by Herrera. 

 Dr. W. A. Orthoni states that he has spec- 

 imens of this rust in his herbarium which 

 were collected in Florida found one year in 

 an exiserimental plat at Miami. His other 

 specimens came from Ealfurrias and other 

 points of the Rio Grande valley, collected 

 seven years ago. From this it is evident that 

 the cotton rust must have been present in 

 Texas and elsewhere, though it did not at- 

 tract the attention of cotton growers or pathol- 

 ogists. JEcidium gossypii E. & E. was first 



1 Correspondence dated July 25, 1917. 



described in Erythea, 5 : 6, 1897. Unfortu- 

 nately the writer was unable to secure a copy of 

 this publication. There seems no doubt how- 

 ever that the present cotton rust is the same 

 as that which was originally described as 

 Ascidium gossypii E. & E. Uredo gossypii 

 Lagh. is another but inconspicuous rust which 

 attacks cotton. This is prevalent in Cuba, 

 Porto Eico and southern Florida, twenty- 

 seven collections of which are found in Dr. 

 Arthur's herbarium. It is very likely that the 

 same rust may be. found to be more wide- 

 spread in the cotton states, although it may be 

 easily overlooked because of its inconspicuous 

 nature. Uredo gossypii resembles very much 

 any other ordinary Uredo. 



A careful search of JEcidium gossypii in the 

 affected district in Texas has as yet failed to 

 reveal the presence in cotton fields of any 

 grasses belonging to the genus Muhlenhergia 

 or Sporoholus. On the other hand there are 

 numerous grasses in that locality which are 

 found to be afPected by various rusts. More 

 recent investigations have disclosed the fact 

 that there are no new infections found on the 

 cotton since the last outbreak was observed. 

 Moreover the secidial stage on the previously 

 affected cotton leaves is now found to have 

 dried, leaving no traces of viable spores. The 

 original spots as well as the old cluster cups 

 are overrun by a varied mycological flora. 

 Just what became of the secidial stage is hard 

 to explain. It is not likely that new infections 

 will start again on the cotton this year. The 

 problem on hand therefore is to determine if 

 possible the alternate host which hibernates 

 the Puccinia stage. Drs. Olive and Arthur, 

 as well as the writer, are now working on this 

 phase, and it is hoped that the Puccinia stage 

 will be found so that the host which hiber- 

 nates it will be destroyed, thereby preventing 

 the further spread of cotton rust. 



In conclusion the writer wishes to express 

 his indebtedness to Dr. J. C. Arthur for help- 

 ful suggestions and for identifications of spec- 

 imens. Grateful acknowledgments are also 

 due Dr. J. J. Marton, agricultural agent of the 

 Texas State Department of Agriculture, for 

 the hearty cooperation and for information on 



