159 
The production of a considerable number of hybrid families 
representing the various possible combinations of these four 
biotypes has demonstrated that their gametic formulae may be aptly 
represented by the conventional Mendelian Symbols, as follows : 
B. bp. heteris . . AB 
B. hp. rliomhoidea . ciB 
B. hp. tenuis . . Ab 
B. bp. Simplex . . ab 
By comparing these formulae with the descriptions of the differ- 
-ent forms it will be seen that A is responsible for the long, 
sharp character of the primary lobe in B. bp. heteris, and the 
attenuation of the lobes in B. bp. tenuis, while B produces the 
division of the leaf to the mid-rib and the resultant definiteness 
of the terminal lobe in both B. bp. heteris and B. bp. rhomboidea, 
the rounded secondary lobe of B. bp. heteris, and the proximal 
and distal incisions of B. bp. rhomboidea. 
Bursa Heegeri has the heteris-iovm of rosette, i. e. with the 
gametic formula AB^ but differs so fundamentally from Bursa 
bursa-pastorts in the characters of the capsules, that if its rela- 
tionship to the latter species were not so obvious on other 
grounds, its capsules would cause it to be placed unquestionably 
in a separate genus. The flat, triangulär or cordate form of the 
hursa-pastoris capsule is too familiär to need description. The 
spur-like valves are lirm, and fall readily at the slightest touch 
when the seeds are ripe. The capsules of B. Heegeri are of oval 
form, surmounted by the short, strong, persistent style, and the 
valves are thin membranous, not the least inflated, and do not 
fall when the seeds are mature. The seeds are liberated by an 
irregulär break in the central region of eacli valve. 
When this original genotype of B. Heegeri was crossed 
reciprocally with B. biirsa-pasforis Simplex, the rosette-characters 
segregated in the Fg, into the four types described above, but 
the Heegeri-tji^G of capsule appeared in only III specinieiis 
among 2540. The distribution of the several characters in the 
F^, are shown in the following table : 
