MATROCLINIC INHERITANCE 
Table V, which shows the range of variation in capsule length in each 
of the four pure forms. The measurements were made in Maryland 
in 1 91 5. In the cases of f. typica and mut. semialta the ten lowest 
normal capsules of the main inflorescence of each plant were used. 
The capsules of mut. debilis were taken from the dehilis plants of a 
polymorphic progeny. They were collected at random, because very 
few inflorescences bore as many as ten good fruits. Capsules of mut. 
hilonga were measured from two different cultures, in order to demon- 
strate the essential identity of this mutation, whether obtained directly 
from f. typica, or as a secondary mutation from mut. dehilis. The 
measurements prove the anticipated identity, or, if anything, give a 
false impression that the secondary mutation is stronger than the 
primary. This impression is due to the fact that at the time the 
measurements were made the secondarily derived mut. hilonga had 
been so short a time in flower that ten full-grown capsules could not 
be obtained from each inflorescence. Six fruits were therefore taken 
from each, and the greater average length which they show in com- 
parison with primarily derived mut. hilonga is due to their lower 
position in the inflorescence. The progeny of primary mut. hilonga 
was arbitrarily divided into a class of weak plants and a class of strong. 
The capsules of these two classes, ten from each plant, were separately 
measured, and the results are recorded in Table V for each class separ- 
ately and for the two classes combined. The discrepancy between 
the two classes was much less than was expected, and indicated 
clearly that the capsules respond less to environmental conditions 
than vegetative parts of the plant. Measurements of any other part 
would have shown a much more marked difference between the 
arbitrarily selected strong and weak plants. 
On account of its relative independence of environmental factors 
the capsule length affords us a more conservative criterion of matro- 
clinic inheritance than the leaf measurements which have already 
been considered. In this respect it seems to be similar to the character 
of flower size, which East^^ has found especially useful in his studies of 
inheritance of quantitative characters in Nicotiana. In Nicotiana 
sylvestris he found that adverse environmental conditions, which 
brought about a shortening of the leaf amounting to three fourths of 
its normal length, did not appreciably change the size of the flowers. 
11 East, E. M., Inheritance of Flower Size in Crosses between Species of Nico- 
tiana, Bot. Gaz, 55: 177-188. 1913. 
