52 BOTANICAL GAZETTE [JULY 
in figs. 17 and 78 it is hard to tell which spore will dominate; and in 
other cases the spore nearest the micropyle functions. The embryo 4 
sac passes through the regular stages to the eight-celled stage. Br- 
_ LINGS (7) figures an embryo sac of Amsonia salicijolia with endosperm : 
surrounded by an absorbing layer, and states that A pocynum andro- — 
saemifolium has no such layer, which we confirmed. A section : 
through the ovules of A. androsaemijolium can hardly be distinguished 
under the microscope from a similar one of Asclepias, so great is the E | 
similarity in minute detail. 
The pollen rolls out of the anthers upon the head, but is pre- 3 
vented by the pericephalous beard from reaching the stigma which — 
is immediately beneath it. An insect having pollen on its proboscis, = 
reaching after nectar, must insert it between the bases of the anthers, — 
on account of the ridges on the corolla and the basal appendages — 
of the stamens. The proboscis in withdrawal naturally slips into — 
the crevices between the stamens and the head. The sticky, glan- — 
dular stigma holds some of the pollen, while the pericephalous beard, | 
acting as a brush, increases the probability of pollen remaining 
4 
4 
ae 
at the stigma (fig. 1). The head above the beard is glandular and a 
the pollen sticky; therefore as the proboscis is withdrawn through — 
the hairs it picks up a load of pollen for the next flower (jig. 4 
KUNTH (6) gives a short account of the manner of pollination. 
The chief facts are the origin of the tapetum from the homologulil 
of the primary sporogenous layer instead of the primary parietal 4 
layer; the gradation between bilateral and tetrahedral microspore — 
arrangement; the absence of a primary parietal cell in the ovule; 
the single layer of cells composing the nucellus; and the great similar- | 
ity in the internal structure of the flowers of Apocynum and Asclepias. 
STATE UNIVERSITY, a WaSsE. * 
LITERATURE CITED. 
p- 37- New Vuk. 3. 
2. WILLE, N., Ueber die Entwickelungsgeschichte des Pollenkérner der Angi 
spermen und das Wachsthum der Membranen durch Intussusception 
Christiania. 1886. | 
3- SCHAFENER, J. H., The development of the stamens and carpels of Tyf 
latifolia. Bot. Gusette 24:93-102. pls. 4-6. 1897. 
1. Courter, J. M., and Cuamsertatn, C. J., Morphology of the Angiosperms. é 
I 
