516 BROOKLYN BOTANIC GARDEN MEMOIRS 
cross of bloom X no-bloom, the F, plants had bloom, but were only 
lightly covered as compared with their ‘“‘bloom”’ parent. In Fs, the 
plants approximated a ratio of 3 bloom: 1 no-bloom as usual, though 
many of those with bloom were lightly covered as in F,. 
Dehiscent and Indehiscent Seed Pods 
The seed pods or seed capsules of Ricinus, in most varieties, are 
dehiscent, the seeds being thrown out of the mature ripe capsule 
with great force. These are known as “poppers” in regions where 
the plant is cultivated commercially. A few varieties have inde- 
hiscent capsules, the seed being retained within the pod for several 
months. This characteristic considerably reduces the cost of harvest- 
ing the beans, as only two or three collections a season are necessary, 
whereas ‘“‘popper”’ varieties must be harvested twice a week or more, 
to prevent loss. The castor-bean plant matures its seed over a very 
long season. The “non-popping”’ variety with which the writer 
experimented has thin-walled, comparatively brittle capsules, while 
all the popping varieties have capsules with thick, leathery walls. 
The dehiscent characteristic is probably due to cells similar to those 
found in the fern sporangium, which rapidly lose their moisture content 
when the capsule matures and contract, thus breaking apart the cap- 
sule and expelling the seed. 
Crosses of ‘popper’? with the ‘‘non-popper”’ variety gave all 
‘“poppers”’ in F; and approximately 9 “popper’’: 7 ‘“‘non-popper”’ in 
F2 (the actual figures being 343 pop.: 259 n.-pop., the theoretically 
expected being 338.4 pop.: 263 n.-pop.). 
In F3, seed from unguarded F» “‘popper’’ segregates gave either all 
“poppers,” or “poppers’’ and “‘non-poppers.”’ 
Seed from unbagged ‘“‘non-popper’”’ F2 segregates produced in most 
cases only ‘“‘non-poppers.’’ The “popper’’ and ‘‘non-popper”’ vari- 
eties involved in the crosses were very distinct, but the F2 populations 
were somewhat difficult to classify, as many of the “‘non-poppers”’ 
would, under very favorable conditions, slightly pop. These were 
usually thin-walled, brittle capsules, showing, perhaps, that the nature 
of the capsular tissue (thick, leathery or thin and brittle) modified the 
“popping” or “non-popping”’ characteristics. On the assumption 
that two pairs of characters are concerned in this cross, each of which 
is primarily determined by the presence and absence of a single factor, 
the results may be interpreted by regarding the “popper”’ character 
as due to the presence of both the factor for popping (A), and the 
factor for thick, leathery capsules (B). In the presence of A and the 
absence of B, the capsules would have thin, brittle tissues, but pop 
slightly, although not sufficiently to class them as “‘poppers.’’ In the 
‘ 
