A CONTRIBUTION TO THE LIFE HISTORY OF 
APOCYNUM ANDROSAEMIFOLIUM. 
THEODORE C. FRYE and ELEANOR B. BLODGETT. 
(WITH PLATE I1) 
It appears that not one of the Apocynaceae, a family of about 1000 
species, has ever been studied carefully in reference to the minute 
morphology of the flower. Considering this in connection with the 
fact that the family stands near the Asclepiadaceae, with their peculiar 
pollen and stigma, it was believed that it deserved investigation. 
Buds and flowers of A pocynum androsaemifolium L. were collected 
in various stages, and the results of their investigation are herewith 
described. 
The order of appearance of the floral whorls is centripetal. The 
calyx shows no peculiarities other than a ruffling of the epidermis 
on the abaxial surface near the base, suggesting a mechanism for 
the folding of the sepals. 
Each petal of the campanulate corolla has on its inner surface 
near the base a ridge (jig. 1, r) running from the midrib diagonally 
outward and toward its base. It is highest at the midrib, and undoubt- 
edly functions as an aid in compelling cross-pollination. The ridge 
arises from the more superficial cells of the leaf, and does not affect . 
the course of the veins. Its meristematic crest forms the cells for its 
enlargement. 
The stamens are peculiar in form, adjusting themselves neatly 
in a ring rather closely applied to the stigmatic head (fig. r,s). At 
the base of each are two long auriculate appendages (jigs. 1, 2, 3, ap) 
extending downwards dorsal to the filament. The sporangia are 
above the insertion of the filament, and do not extend into the appen- 
dages. The loculi open on their inner surfaces, somewhat laterally, 
by longitudinal slits, and immediately beneath them is a beard of 
epidermal hairs extending transversely across the faces of the anthers, 
forming a ring around the stigmatic head (figs. 1, 2, b). These hairs 
meet similar ones from a ring around the head, thus preventing 
pollen from rolling into the base of the flower. 
15] 49 
Mo. Bot.Garden 
1906 
