98 CARNEGIE INSTITUTION OF WASHINGTON. 



for the production of a generic group, or at the least for a widely dis- 

 persed, closely related group of "species" in nature. 



Report on Cactus Investigation, by N. L. Britton and J. N. Rose. 



Subsequent to the closing at the end of 1916 of the five-year period 

 devoted to field, greenhouse, and herbarium investigation, Dr. J. N. 

 Rose, Research Associate during that period, returned to the United 

 States National Museum, but by permission of that institution has 

 given all his time to the preparation of manuscript for the monograph 

 of the Cactacese, in cooperation with Dr. N. L. Britton, director-in-chief 

 of the New York Botanical Garden. This monograph has been ren- 

 dered much more complete than was otherwise possible by large collec- 

 tions obtained by Dr. J. A. Shafer last winter in Argentina, Paraguay, 

 and Bolivia, thus furnishing much valuable material for illustration 

 and adding greatly to our knowledge of the cactuses of South America. 

 Dr. Britton commissioned Dr. Shafer for this work. 



Analysis of a Potato Hyhrid, Solanum fendleri X S. tuberosum {"Salinas"), 



by D. T. MacDougal 



The wild potato of Arizona, S. fendleri, which is to be found on the 

 mountains above 5,000 feet, produces a small tuber and endures the 

 extremes of the climate of that region. It has been carried through the 

 acchmatization cultures at Tucson and at the Coastal Laboratory. 

 Flowers were finally produced at Carmel in 1913 and 1914, at the time 

 the domestic variety of that region was in bloom. A cross was obtained 

 in 1914 and the second generation, represented by about 1,000 plants, 

 was brought to maturity in 1917. The first generation is intermediate 

 between the two parents and produces tubers about two or three 

 times as large as the wild parent. A lineal series of these tubers will 

 be cultivated in order to test the matter of vegetative mutation. The 

 second crop in this line has already matured. 



The F2, or second generation, includes a number of individuals which 

 appear to be identical with the wild parent. Whether the domestic 

 parent is similarly represented can not be definitely ascertained for 

 another season. Many recognizable qualities of both parents are 

 represented in a large number of intermediate forms. 



Professor G. H. ShuU, of Princeton University, has undertaken 

 a genetic analysis of the domestic parent, with preliminary results 

 which indicate its hybrid constitution very clearly. 



The cultures of the hybrid in 1917 include lots of plants grown on 

 the Santa Catalina Mountains, Arizona; at the Citrus Experiment 

 Station, Riverside, California; Desert Laboratory, Tucson, Arizona; the 

 Coastal Laboratory, Carmel, CaUfornia; a ranch at 1,000 feet elevation 

 a few miles from Carmel, and on the testing-grounds of the Department 

 of Plant Breeding of the University of California, Berkeley, California. 



