parr ut] THE MECHANISMS OF FLOWERS. — 523 
Both females and males are wingless, and the males are dis- 
tinguished by having a pair of long appendages at the side of the 
abdomen, which are attached to the stigmata, and probably protect 
them from the brown sticky pulp within the fruit (460). 
Paul Mayer has investigated the wasps of numerous other old- 
world species of figs, mostly from herbarium specimens. In some 
species of Ficus and Sycomorus he has found Blastophaga and 
Sycophaga together, but the whole number of species of wasps 
was very small. On the other hand, the Brazilian figs, of which 
Fritz Miiller examined ten species in his own neighbourhood 
(Blumenau, province of St. Catharina), possess an astonishing 
variety of wasps belonging to the same family of the Agaonide ; 
some of these belong to the genus Blastophaga, some to a genus 
like Jchneumon. Many are adorned with metallic colours, which 
fact suggests a longer stay in the open air. In point of fact, most 
of the figs which Fritz Miller studied, flower only once a year, 
so that many of these wasps must, in order to lay their eggs, seek 
another tree of the same species which is just beginning to flower 
at the time when the figs are ripe upon the tree where they them- 
selves were developed, In the case of many species of these wasps, 
at least four migrations are necessary in the course of the year. 
In these figs, the old inflorescence from which the wasps issue 
bears only male flowers, and the young inflorescence which they 
enter bears only female flowers. Self-fertilisation is thus rendered 
impossible, and separate individuals are regularly crossed. The 
fruit becomes sweet and in many cases gaily coloured when the 
seeds ripen, and parrots which feed on it help to disseminate 
the seeds (460). 
Orv. JUGLANDACE &. 
Juglans cinerea, L., in the United States is moneecious, and, like 
J. regia, L., in Europe, is sometimes proterandrous and sometimes 
proterogynous (Darwin, 167, 2nd ed.). 
Orv. CUPULIFERZ. 
The plants of this order also are anemophilous, but not quite 
excluded from insect-visits, On February 29, 1868, in fine 
weather, I saw numerous honey-bees busy collecting pollen on the 
male catkins of the hazel, but none settled on the female catkins. 
In many places proterandrous and proterogynous plants of the 
hazel (Corylus Avellana, L.) occur. together. 
