212 Blakeslee. 



production of purple cones. On account of the colors, which they 

 assume when treated with strong alkali, the two types are called 

 respectively Black Yellows (BY) and Red Y^'ellows (BY), 



While the Yellow Daisy is interesting- on account of its great 

 variability in the field, it is ill adapted in many ways for breeding 

 experiments. The numerous florets on the cone are too small to be 

 handled individually, hence self pollination can not readily be excluded. 

 Self pollination, however, in most cases does not lead to self ferti- 

 lization, since the species is predominately self-sterile. Only in des- 

 cendants from a single plant (the „chocolate" line) have any considerable 

 number of plants been found to be self-fertile. Thus, out of 1075 

 offspring from our original Black-Yellow plant used in crosses as a female 

 parent, there was only a single seedling that could be considered the 

 result of selfing. Heads bagged before the florets open can be pollinated 

 with little fear of interference from the pollen of the female parent, 

 unless the latter contains „chocolate." blood. The greatest drawback to 

 the use of Rudbeckia as material for genetic study is the decreased 

 vigor and tendency to intersterility between sibs, which is connected 

 with inbreeding. As a result it is often difficult to find compatible 

 combinations between plants even in the Fi generation and the amount 

 of viable seed from a given cross may be meagre. The number of Fä 

 plants are therefore fewer than would have been expected from the 

 crosses attempted. 



II. Origin of Yellow coned races. 



a) Black Yellows. The first plant with j^ellow cone observed 

 by the writer came from open pollinated seed from a plant brought in- 

 to the Botanic Garden of the Conn. Agric. College in 1910. Its parent, 

 selected on account of a light red cone (probably grade t or d) had 

 been found in a nearby meadow together with a number of other striking 

 variants such as doubles, mahoganies and quilled types. This plant 

 (R23) is the origin of all the Black Yellows in our cultures. No other 

 Black Yellows have been found by us, although for many years the 

 fields in the vicinity of Storrs have been thoroughly searched for such 

 variations. 



b) Red Yellows. Red Yellows have been found in two localities 

 near Storrs, Conn. In one, about a mile from the Botanic Garden, only 

 a single plant (V91) was observed; in the other locality, 6 or 7 miles 

 from the college, mthin an area of not over an acre, several Red Yellows 



