STUDIES IN TERATOLOGICAL PHENOMENA 
25 
Cruciferae by artificial parasitization with Phytoptus, and, according 
to Hus (1908), Molliard caused the formation of double flowers by 
mechanical irritation. From these facts, one may conclude that 
double flowers may result from many different causes. 
In Nicotiana, petalody arose in at least two dozen plants of four 
or five hybrid families on which observations were being made for 
other purposes. The pure species from which these hyrbids were 
derived, while under observation for five years, never developed petal- 
ody. Further, this abnormal condition was never observed in Fi 
hybrid generations, although thousands of flowers were examined. 
Two of these abnormal plants were self-fertilized, and the progeny, 
grown under approximately the same environment as the mother 
plant, reproduced the character, showing it to be a hereditary and not 
an induced phenomenon. One of the races was derived from an F2 
segregate of N. langsdorffii X N. forgetiana. The expression of the 
character in the stamens was very variable. Table i gives a general 
Table i 
Number of affected stamens per flower i 2345 Total 
Number of flowers i 14 4 6 25 
idea of the extent of this variability among the different flowers of the 
mother plant. The progeny, over 100 in number, all possessed the 
abnormality. The throats of the corolla tubes in some plants were, 
however, almost packed with anomalous stamens; while in others, 
perhaps only a single stamen was malformed. An examination of the 
progeny plant by plant for differentiating characters showed that 
segregation in flower color, habit of plant, leaf shape, etc., had occurred, 
indicating that the mother plant was heterozygous for a large number 
of factors. 
The other race of these anomalous stamen-bearing plants was 
derived from selfed seed of a plant which appeared to be N. langsdorffii 
grandiflora. The variability of the abnormal character is shown in 
Table 2. In 191 2 under the same field conditions, 70 plants were 
Table 2 
Affected stamens per flower i 2 3 4 5 Total 
Number of flowers i 20 4 25 
grown from selfed seed of this mother plant. The inspection of these 
70 plants showed the parent to have been homozygous in all its 
