APRIL, 1900. GRAENICHER— FERTILIZATION OF FLOWERS, ETC. 
79 
simple structure, bearing- no perianth, and being arranged in 
oblong cylindrical catkins. In this species the male or staminate 
flower consists merely of two stamens, arising from the base of a 
scale, and is furnished with a nectar-gland at the base. The 
female or pistillate flower is constructed exactly on the same plan, 
having a pistil instead of the two stamens. It is an easy task for 
any flow^er-visiting insect to gain access to the entirely exposed 
])oilen, as well as to the nectaries of these simple flowers, and this 
fact, together with the rich supply of pollen and nectar in the 
numerous flowers, explains the frequency with which they are 
visited. Another point of advantage in attracting insects to the 
flowers, is the opening of the flowers of Salix discolor and of a 
few other early species of Salix before the green leaves of the 
stem appear. It is evident that the catkins of such a species are 
more conspicuous than those of a species producing the green 
leaves in advance of the flowers. 
According to Kerner's (6) statements, the majority of 
dioecious plants are proterogynous. In referring to willows, this 
author mentions four European species, in which proterogyny has 
l)een ol)served, the pistillate flowers appearing from one to three 
days earlier than the staminate flowers. This condition of affairs 
favors, in the opinion of Kerner, the production of hybrids, as the 
very first pistillate flowers of such a species can not, during the 
first two or three days of their existence, be supplied with pollen 
of the same species, but may be fertilized by pollen from another 
species, whose staminate flowers are blooming at that time. From 
observations on Silax discolor during the last three years, I am 
satisfied that this species is proterogynous, the female flowers 
opening at least one day, and, as a rule, two days in advance of 
the male. In this species proterogyny can have nothing to do with 
the production of hybrids, as Salix discolor is oiu* earliest willow^ 
and, therefore, no staminate flowers of any other species are on 
hand during the proterogynous period of this plant. 
As has been stated previously, the floAvers of this willow are 
al)undantly visited by a great variety of insects, and, on looking 
over the following list of visitors of Salix discolor, we come across 
the majority of anthophilous insects flying in early spring. 
A. Hymenoptera. 
Apidae : (i) Apis incllifica, L. V s. and c. p. (2) Boinbns 
Ed'wardsii, Cr. $. s. ; (3) B. Virginicus, Oliv. 9, s. ; (4) B. separa- 
fiis, Cr. V, s. ; (5) OsiJiia lignaria, Cr.cf ?, s. ; (6) O. atriventris, 
Cr.9 , s. ; (7) Nomada integerrima, DT.^^, s. ; Andrenidae : (8) 
(6) A. Kerner von Marilaun. Pflanzenleben, Yd. H, pp. 31 1 -31,1. 
V Wo/ker; c^Male; V Female; s Sucking; c p Collecting: Pollen : f p Feeding on Pollen. 
