344 



jiud methods of pollenization iu 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 snmnied up, shows that the 

 disposition of the sexes and the modifications in form of the infiores- 

 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 proterosiy- 

 nous, 1. e., the female element of the llowers or tlower-spike precedes 

 the male in time of blooming. To this class most, if not all, of the 

 Philodendrons belong. 



Among those aroids in Avhich the upper portion of the s|)adix 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 res|)ect to these arrangements. Those species in which 

 the spathe is open and the entire s^^adix free, may be fertilized by 

 insects of many kinds {fnd even by snails. The odors given off by 

 aroids having an inflorescence of this character are otten fragrant, or 

 at least not oflensive 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 Luc'dia 

 ccesar, the common blow fly, or carrion beetles, Saprinufi 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 oft* 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 oft" pollen adhering to their bodies. It is 

 inobable, however, that in the tropics aroids, in which the spadix is 

 Avholly 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 nmtually 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- 



