EFFECTS OF SELECTION ON ALKALOIDS IN BELLADONNA. Ihab 
for cross-pollination and to almost exclude the probability of close fertilization in 
individual flowers. However, the feeding habits of the principal pollinating insects 
(mostly night and day flying lepidoptera), which visit in turn many open blooms | 
on the same plant, may tend after all to promote self or close pollination on a consider- 
able proportion of blooms on any given plant. If all the seeds in a single fruit should 
mature and produce plants with a high alkaloidal content or any other transmissible 
%400 
Y.99 
NZ 
Y.70 
Y.60 
S57 g 
8 50 2 
R ; 
S.20 8 
s 70 
a 
q 23h) H) 7W (6) FW (a) 6W) 
Fic. 7.—Diagram showing the alkaloidal content of the leaves of first-generation belladonna plants from 
close-pollinated and cross-pollinated selected parents at two stages of growth during the second season, 
1914. The percentages indicated represent the average of all the individuals from each parent plant: 
a, Plants from close-pollinated parents; 6, plants from cross-pollinated parents. 
feature of the seed parent, it does not necessarily follow that the pollen of another 
individual possessing this feature in a lesser degree might not have a reducing effect 
on the desired characteristic, as the seeds planted may easily be the result of actual 
close pollination between different blooms of the maternal plant or even of self- 
fertilization of an individual bloom. It is but fair to suppose that a majority of the 
seeds of a given plant may thus be self-pollinated, notwithstanding nature’s adapta- 
tion of the blooms for crossing, unless it has been made apparent that belladonna 
blooms are not receptive to their own pollen or to that of 
flowers on the same plant, but must be fertilized by Ne 
pollen produced by another individual. This conclusion 
has not been demonstrated by any controlled experiments 
that have come to my knowledge. 
SECOND-GENERATION PLANTS FROM CROSS- 
POLLINATION. 
Up to this point the investigation has dealt owe ee 
entirely with first-generation plants. During Zio) We) 61a) 
the season of 1914 analyses were made of plants |. , Dike oe 
ie : = re) a 
which represented the second generation of the average sietida loa net 
original selected individuals. The seed which — 2! the individual belladonna 
; plants from each parent for 
furnished these plants was secured from the the second season, 1914: 
followin first-seneration plants im the fall of  % Flents tom  close-poll 
nated parents; 6, plants from 
1913: 6w,, 6Wy, 6Wy,, 7W;, 22, 23, 31, 3g, 37, 342, cross-pollinated parents. 
34,, 34,,35;. The plants from 6w and 7w were 
selected as types of high alkaloid-yielding plants, those from 2 as 
medium, and those from 3 and 34 as low alkaloid-yielding types. The 
seed was planted in the greenhouse at Arlington, Va., in January, 1914, 
and the plants were transferred to small pots when of suitable size. 
