A cheiiiioal metliod of distinguishing genetic types of yellow cones in Rudbec.kia. 213 



have been discovered. The first year they were observed too late to 

 l)e used iu crosses and the plants taken to the Botanic Gard(m failed 

 to recover from transi)lantin<»-. The next season other Red Yellows were 

 found at the same station and are represented by plants (V83) and (V85) 

 which with the other Red Yellow (V91) and the Black Yellow (R23) 

 have been kept under cultivation in clones throughout the progress of 

 the breeding experiments. 



III. Chemical tests. 



The breeding behavior of our yellow coned plants indicated that there 

 were among them two distinct color types, although these types could 

 not be separated by mere inspection. It seemed a reasonable conjecture 

 that the two types might differ somatically in their chemical constitution 

 sufficiently to show different reactions to chemical tests if the proper 

 reagent could be discovered. Accordingly cones of the two types were 

 tested with different compounds, chosen largely at random. 



Table 1 shows some of the reagents used, which gave different 

 reactions with the two types. In addition a number of other chemicals 

 were tried which gave little or no differentiation between the two forms. 

 These include ammonium hydroxide, oxalic acid, stannous chloride, 

 potassium ferrocyanide, lead acetate, hydrogen peroxide, Phenolphthalein, 

 tyrosin, and hydrochinon. 



The alkalies KOH and NaOH gave the best differentiation, the latter 

 perhaps slightly better than the former. In our tests we have used 

 more commonly KOH in 8 normal aqueous solution. Fresh cones with 

 opened florets are placed in the concentrated alkali and the reaction is 

 evident in about one minute. The scales of the chaff which subtend 

 the florets are not differentially affected by the treatment and hence 

 open florets must be available for a test. It does not seem possible to 

 obtain reactions with old dried heads. Hence the tests have always 

 been made in the field with fresh material. In the accompanying colored 

 diagram the cones in parentheses represent fairly well the colors assumed 

 by the Black Y^ellows and Red Y'ellows respectively when treated with 

 strong KOH. 



Seedlings of both Black Y^ellows and Red l^ellows have no trace 

 of red in stems or leaves characteristic of purple coned plants. Sections 

 of these parts of yellow coned plants were tested with various reagents 

 but were not found to give distinctive chemical reations which could be 

 used in separating the two types. The lack of any red color in a 



