igisl 



BARTLETT— MUTATION IN OENOTHERA 



87 



In 0. pratincola 



A well-grown plant, is i . S na. high, 

 and loosely branched. 



The basal branches are frequently 

 simple. 



The flowering time lasts about six 

 weeks. 



The lax terminal spike often be- 

 comes s-6 dm. long (see fig. 1). 



The lateral branches below the 

 terminal spike are few in number 

 and become 4-5 dm. long. 



The lowest bracts of the upper 

 lateral spikes are ovate, and grade 

 upward to lanceolate. 



The calyx segments are so sparsely 

 pilose as to appear practically gla- 

 brous. 



The hairs of the calyx segments are 

 about 1 mm. long, thick-walled, acute, 

 with multicellular tuberculate bases. 



In 0. numismatica 



A well-grown plant, is about 1 m. 

 high, and densely branched. 



The basal branches bear tertiary 

 branches and resemble the main 

 stem. 



The flowering time lasts only about 

 two weeks. 



The dense terminal spike is about 

 2 dm. long in fruit (see fig. 2). 



The lateral branches below the 

 terminal spike are numerous and are 

 seldom over 2 dm. long. 



The lowest bracts of the upper 

 lateral spikes are nearly orbicular 

 and grade upward through oblong 

 to lanceolate (see fig. 2). 



The calyx segments are closely 

 and finely pubescent. 



The hairs of the calyx segments are 

 less than o. s mm. long, and belong 

 to two types: (i) an acute thick- 

 waUed type without tuberculate bases, 

 and (2) a thin-walled, round-ended, 

 clavate or cylindrical type. 



Technical diagnoses of these two species, together with a discus- 

 sion of their possible relationships, have been published elsewhere.'^ 

 0. pratincola appears to be a frequent plant in the North Central 

 States. 0. numismatica, on the contrary, is known only from 

 Lexington and may well be a local species, possibly derived by 

 mutation from O. pratincola. Its close resemblance in certain 

 characters to one of the mutations of 0. pratincola is pointed out 

 elsewhere in this paper. 



The mutations of "Lexington C" 



Seeds from four of the parent plants of 0. pratincola which had 

 been selected at Lexington were planted early in the spring of 19 13. 



'' Bartleit, H. H., Twelve elementary species of Onagra. Cybele Columbiana 

 1:37-56. 1914. 



