434 BROOKLYN BOTANIC GARDEN MEMOIRS 
from the suppression of dominant characters it will be obvious that 
these ratios are modifications from a higher ratio (e. g., 15 : 1) rather 
than from the 3 : I ratio to which the empirical results in fact more 
closely approximate. 
A new attempt to test the constitution of the rosette in the shep- 
herd’s-purse of Tucson, was made with seeds received from Dr. 
Forrest Shreve on November 29, 1914. The same care was given to 
the culture of the families involved in this new experiment as was 
exercised in those recorded in Table 2. The better greenhouse facili- 
ties available at Princeton as compared with those at Cold Spring 
Harbor, where the previous cultures had been grown, made it possible 
to secure a closer approximation to the expected ratios, as seen in. 
Table 3, the deviation being the same as before 7 direction but less 
in amount. 
TABLE 3 
The Composition of the F, Progenies from a Cross between Bursa bursa-pastoris heteris 
from Tucson, Arizona, and B. Heegert simplex grown at Princeton University 
BSE umber heteris \Phomibeddea | tenuis simplex | Ratio 
P; | F, F AB | aB | Ab a B:b 
ee 14387 15423 143 76 ee ee 11-53 25 
1542 I 2 I | “75001 cur: 
Site ale 5424 Whe ae 7 ‘ if 
NOtAlSmrtsredeece canter te aeaie etek 157 83 13 9 LO:Ol0 
BPO. apch 3s eine | 85 OF) -aleeei2 4 15.00: 
Fortunately for genetical studies on the rosette characters of 
shepherd’s-purse, such extensive suppression of characters occurs in 
nearly all of the other biotypes which have been under observation, 
only as a result of distinctly unfavorable environmental conditions. 
The study of a large number of these biotypes from other regions, 
in crosses with B. Heegert simplex, has brought to light several other 
cases of probable duplication of the B factor, as shown in Table 4. 
The cultures in Table 4 also show for the most part distinctly 
defective ratios, due certainly in the main to the fact that they were 
being grown in an extensive study of the capsule determiners, and that 
in consequence suitable conditions were not provided in many cases 
for full development of the rosette characters. Here and there a 
ratio closely agrees with the expected Fy, ratio, 15 : 1, the best fits 
being seen in certain families grown from seeds from Bremen, Germany. 
By chance these families from Bremen grew under more favorable 
conditions than many of the other cultures listed in this table and 
this fact doubtless explains in part why they show a closer approxima- 
