344 
and methods of pollenization in the Aracese (Botan. Jahrb., iv, pp. 
341-352, 1883), in which, in addition to his own profound researches, those 
of all previous writers on this subject are summed up, shows that the 
disposition of the sexes and the modifications in form of the inflores- 
cence in this family are exceedingly varied and complex. Contrivances 
adapted to insure cross-fertilization abound. A great number, per 
haps the majority of the species that have been noted, are proterogy- 
nous, i. e., the female element of the flowers or flower-spike precedes 
the male in time of blooming. To this class most, if not all, of the 
Philodendrons belong. 
Among those aroids in which the upper portion of the spadix bears 
male and the lower part female flowers, Engler notes eleven distinct 
arrangements of the sexes upon the spadix, or modifications of the 
spathe with respect to these arrangements. Those species in which 
the spathe is open and the entire spadix free, may be fertilized by 
insects of many kinds and even by snails. The odors given off by 
aroids having an inflorescence of this character are often fragrant, or 
at least not offensive to man, and are such as attract most insects, and 
the list of species which have been observed to enter the spathes is a 
very extended one. Some aroids of this class on the other hand exhale 
the odor of carrion and are visited by carrion insects, such as Lucilia. 
ccesar, the common blow fly, or carrion beetles, Saprinus nitidulus, etc. 
Many aroids, as noted by Engler, have the spathe constricted in 
various ways so as to partly inclose the spadix and divide more or less 
completely the portion bearing male from that bearing female flowers. 
The fertilization of the inflorescence in such cases must be effected by 
those insects which are adapted to creep through narrow apertures or 
to live in dark quarters, and the majority of insects which frequent 
ordinary flowers are excluded. The pollen in aroid flowers of this class 
is usually given off in vermiform masses, and is more or less glutinous 
and not dry as in open flowers. The odors in the few cases in which 
they have been noticed are said to be disagreeable or peculiar. 
In Pinellia tuberifera Ten. the spathe is constricted, so that an aper- 
ture only one square millimeter in dimensions connects the male with 
the female chambers. Breitenbach and Engler also observed that 
swarms of small gnats passed freely through the minute opening, and 
that they were able to carry off pollen adhering to their bodies. It is 
probable, however, that in the tropics aroids, in which the spadix is 
wholly inclosed or difficult of access, are fertilized for the most part by 
sap-beetles. And when the life-histories of the numerous tropical 
species of Cillseus, Macrostola, Brachypeplus, Conotelus, and their near 
allies, shall have been made known, many of them will no doubt be 
found to be connected with the economy of some aroid, the plant and 
the beetle being mutually dependent the one upon the other. 
No entomologist, as far as I am aware, has given any attention to 
the fertilization of West Indian aroids by insects, but Salle and Fleu- 
