372 
T. H. GOODSPEED AND R. E. CLAUSEN 
Spread of corolla may drop 6 mm. and the average length as much as 
4.5 mm. In such a case for flowers on individual plants the difference 
will be greater still. 
2. The Fi N. Tabacum X N. sylvestris hybrids possess the short- 
lived perennial habit of N. sylvestris and will bloom a second and third 
season on their own roots. The first flowers produced the second 
season were of approximately the same size as the first flowers produced 
the first year and were considerably larger than the flowers produced 
toward the end of the first period of flowering. The difference in size 
was greater for spread of corolla than for length of corolla. 
3. The removal of all open flowers during the normal flowering 
season will keep up the flower size to nearly that of the first flowers 
produced and in some cases will double the life of the plant. There 
is a distinct relation between the presence of developing seed on an 
inflorescence and the size of the flowers produced thereupon. This 
relation is analogous on the one hand to the agricultural practice of 
"topping" tobacco plants to favor vegetative luxuriance and on the 
other hand to the restricting of the vegetative growth in cotton to 
favor an earlier development of fruiting branches and thus an earlier 
crop. 
4. Flowers that are apparently fully expanded but with the 
anthers unopened are smaller than fully opened flowers after anthesis. 
Similarly there is a striking difference in the size of flowers produced 
on a terminal inflorescence that is almost through flowering and on a 
lateral inflorescence that is just in full bloom. This difference holds 
for the semi-sterile Fi hybrids as well as for the parent N. Tabacum 
var. macrophylla where many seed capsules are developing on the 
older inflorescences. Spread and length of corolla are equally di- 
minished in size when flowers on older terminal inflorescences are 
compared with those on lateral inflorescences in full bloom. With 
reference to the difference in size of flowers before and after the dehis- 
cence of the anthers, the spread of corolla is relatively more greatly 
increased after anthesis than the length. 
5. The flowers on cuttings taken from plants in the field and grown 
in pots in the greenhouse are smaller than those borne on the plant 
from which the cuttings were taken. This is more strikingly evident 
in the case of spread than in the case of length of corolla. 
6. Under favorable and unfavorable conditions of greenhouse cul- 
ture flower size will vary distinctly and in the same direction as vegeta- 
tive characters under such conditions. 
