DEPARTMENT OJ* EXPERIMENTAI, EVOIvUTlON. 



91 



The cultures of Indian corn were somewhat enlarged to allow a fuller test 

 of the relative vigor of pure-bred types and their hybrids. The results have 

 been consistent throughout, the self-fertilized families appearing to have 

 reached a certain low state of vigor which is not further decreased by con- 

 tinued self-fertilization. Crossing between individuals belonging to a single 

 pure type appears to give no advantage over self-fertilization, while all 

 crosses between individuals belonging to distinct types are of superior vigor. 



In Shirley poppies the color-characters have been followed through another 

 generation and several of the unit-characters involved have been recognized. 

 Several pedigrees have shown the segregation of the characters into homozy- 

 gous types. Many crosses have been made in order to determine the compo- 

 sition of each type which has appeared, and especially to compare each with 

 the wild type of Papaver rhaas, from which the Shirley poppies are reputed 

 to have sprung. 



The greatest amount of space and attention have been given to studies of 

 heredity in Lychnis alba, largely with reference to problems of sex-deter- 

 mination and sex-heredity. The rare occurrence of hermaphrodite mutants 

 in this usually dioecious species has provided excellent material for the study 

 of certain phases of the sex-problem. The great differences in the sex- 

 ratios in different families and the usual excess of females over males present 

 other problems of quite general interest and importance. Besides making 

 observations on over 12,000 individuals of this species during the past season, 

 more than 230 definite crosses have been made for the continuation of the 

 work next year. 



The comparative cultures of cross-fertilized and self-fertilized Oenotheras 

 have been continued and the tests of elementary species in Lactuca canaden- 

 sis, Brigeron ramosus, and Oenothera cruciata have further demonstrated 

 their permanence and distinctness. 



A census of the cultures for the past season shows the following results : 



Chrysanthemum leucan- 

 themum 



Erigeron ramosus 



Helianthus annuus 



Lactuca canadensis 



Lychnis alba 



Lychnis chalcedonica 



Lychnis haageana and 

 varieties 



Lychnis (Viscaria) spl en- 

 dens 



Nigella damascena 



Oenothera cruciata 



Oenothera gigas 



Oenothera lamarckiana 



Oenothera lata 



Oenothera nanella 



Oenothera rubrinervis. . 

 Oenothera scintillans. . . 



Oenothera spp 



Papaver rhceas 



Verbascum blattaria 



Verbena stricta 



Zea mays 



Total 



Dr. J. Arthur Harris has had general oversight of the preceding cultures 

 during Dr. ShuU's absence. In addition to this work he has been making 

 preliminary observations on species of Cucurbitacese, Passifloracese, Malva- 

 ceae, and Solanaceae, to determine their fitness for experimental work before 

 serious and detailed studies are undertaken. He has also continued work 

 along four other lines as follows : 



