148 Shaw—Structure of the Flowers in 
5. The microspores of the evident flowers undergo a great 
increase in size at the time of flowering ; the same is true toa 
less degree of the microspores of the two other types of flower. 
6. Contrary to the condition described for the other cleis- 
togamic flowers, the walls of the microspores are very thick. 
7. A canal is present in the pistil leading from the ovarian 
cavity to the exterior. At the base of the style the lumen 
is sometimes filled by hairy outgrowths from the surrounding 
tissue. A similar condition is found in P. pauczfolia. 
8. Glandular hairs, found sparsely on the ovary of the evi- 
dent flowers, are present in great abundance on that of the 
subterranean ones, pointing to specialization of some kind, 
possibly a capacity for absorption. 
g. Theindurated portion of the testa is derived from the 
inner cell-layer of the primine. 
10. The chasmogamic flowers of P. paucifolia exhibit a 
condition of initial gynandry combined with the complete 
coalescence of stamens and petals. 
11. The hypothesis that cleistogamic flowers are developed, 
to preserve the species when the chasmogamic ones fail, is un- 
satisfactory, because these are produced each year abundantly. 
12. The hypothesis that this development is due to lack of 
light or similar causes is probably partially true, but is insuf- 
ficient, because cleistogamic flowers are produced in great 
abundance on healthy plants in the warm and sunny period 
of midsummer. 
13. Neither can this development be explained as a device 
for developing protected fruits, for although the plant suffers 
from grazing animals, these aérial flowers appear among the 
foliage where the danger is greatest. 
14. The cleistogamic flowers, like those of other species, 
develop seed more rapidly than do the conspicuous ones. It 
is believed that the purpose of their existence is the economi- 
cal and speedy production of seed, 
