102 CARNEGIE INSTITUTION OF WASHINGTON. 



Some rather complex pattern types have been extracted, and these 

 are in some cultm^es already giving more complex conditions, so that 

 there is no means of knowing how far the process will go. The tests 

 being made of these alterations at Chicago are under standard and 

 uniform conditions, in which at the least the usual environmental 

 action is ehminated, but in spite of this the apparent orthogenetic 

 progression continues by what appear to be some series of internal 

 operations that are gradually working themselves out, giving stable pure 

 lines during the process. Collectively the series shows a wide array of 

 new conditions due, as far as present evidence goes, to the introduction 

 of some new gametic factors and the gradual production of the possible 

 combinations between these and the existing factors. 



No new cultures have been introduced at Tucson during the year, 

 owing to the derangement of the investigation by the building opera- 

 tions and the poor transportation to and from the tropical areas whence 

 many of the desired introductions come. The pohtical conditions in 

 Mexico also seriously hinder the investigations, it being quite impos- 

 sible to obtain from the southern part of Mexico materials much needed. 



The general oversight and care of the experiments has been continued 

 through the year by Mr. J. G. Sinclair. 



Relationships and Distribution of the CadaceoB, hy N. L. Britton and J. N. Rose. 



At the time the report on the progress of this investigation was 

 written last summer, Dr. Rose was engaged in exploring the cactus 

 deserts of western South America, one-half of the expense of this expe- 

 dition being borne by the New York Botanical Garden. He returned 

 in November 1914, having secured notes, photographs, specimens, and 

 living plants of most of the cacti which inhabit Peru, Bolivia, and Chile; 

 his field studies and subsequent museum work have demonstrated 

 the existence in these regions of several hitherto unrecognized genera 

 of Cactaceae and a number of undescribed species. The collections 

 made by Dr. Rose were extensive, and their study and description 

 occupied much of the time of both research associates during the winter 

 and early spring, but substantial progress was also made in writing 

 descriptions of other cacti, preparatory to the pubUcation of the mono- 

 graph of the family. Many additional drawings and paintings have 

 also been secured. 



Dr. Britton gave part of the month of March 1915 to further studies 

 of the cactus region of Porto Rico, visiting most of the area inhabited 

 by these plants along the southern coast of that island and obtaining 

 additional information on geographic distribution. 



In last year's report reference was made to the desirabiUty of explor- 

 ing also the cactus regions of eastern South America, and thi'ough a 

 continuation of cooperation with the New York Botanical Garden Dr. 

 Rose proceeded in May to eastern Brazil, making Bahia his first base of 



