160 DISPERSION OF POLLEN BY ANIMALS. 



Each male flower is composed of one or two — rarely from three to six — stamens, 

 which are supported by scales, and are borne on a short stalk (fig. 240^-). lu 

 many species, as, for instance, in Ficus pumila, the stamens are spoon-shaped 

 and have the anthers imbedded in the concavity of the spoon (figs. 240^ and 240^). 

 The female flowers possess a unilocular ovary containing a single ovule. The style 

 is inserted rather to one side of the ovary and terminates in a stigma, which is 

 variously formed. At the base of the ovary are to be seen a few small scales 

 which vary in number, and may be regarded as the perianth (see figs. 240" and 

 240^^). Many species have two kinds of female flower in the same urn or 

 synconium, viz. some with long styles and developed stigmas, and some with 

 shorter styles and abortive stigmas. The latter are called gall-flowers for a reason 

 that will presently be explained (fig. 240^*). The relative distribution of male and 

 female flowers is very different in different species. In the inflorescences of the 

 India-rubber Fig (Ficus elastica), figured on p. 755, vol. i., the male and female 

 flowers are apparently mixed together promiscuously ; in that of Ficus pumila 

 (fig. 240^) female flowers only are found in the lower part of the cavity, and 

 only male flowers near the mouth. This distribution is the most usual, but yet 

 another difference exists in respect of the number of male flowers. In the 

 synconia of many species the male flowers occur in large numbers near the orifice, 

 whilst in others there are very few — indeed it even happens sometimes that there 

 is an entire absence of male flowers in one inflorescence or another. In many 

 species some individuals only produce inflorescences containing female flowers, 

 and other individuals inflorescences with male flowers near the orifice and Avith 

 female flowers lower down. But the most remarkable circumstance of all is that 

 in the inflorescences of many species all or most of the female flowers below the 

 male ones are transformed into gall-flowers. This is the case, for instance, in the 

 common Fig-tree (Ficus Carica) cultivated in Southern Europe, a species which 

 includes two kinds of individuals, viz. those whose inflorescences contain female 

 flowers only, and those whose inflorescences contain male flowers near the opening 

 and gall-flowers lower down (cf. figs. 240 ^° and 240 ^^ ). The former individuals are 

 known by the name of Ficus, the latter by the name of Caprificus. 



We have now to consider what may be the meaning of the gall-flowers. As the 

 name indicates, not fruits but galls are produced from these modified female flowers, 

 and this happens in the following manner. There is a small wasp belonging to the 

 Chalcididse, a family of Hymenoptera (cf. fig, 240^^ and 240^^), already referred 

 to as Blastophaga grossorum, which lives upon the Fig cultivated in the south of 

 Europe. This insect passes into the cavity of the inflorescence through the orifice, 

 and there sinks its ovipositor right down the style-canal of a flower, and deposits 

 an egg close to the nucellus of the ovule. The white larva developed from the egg 

 increases rapidly in size and soon fills the entire ovary whilst the ovule perishes. 

 The ovary has now become a gall (fig. 240^*). When the wasps are mature they 

 forsake the galls. The wingless males are the first to emerge, and they effect their 

 escape through a hole which they bite in the gall. The females remain a little 



