208 NATURAE WS CIEN CE. Marcu, 
by a separate pollen-grain; and but very few pollen-grains could be 
found in the female figs. Although it is possible that in some cases 
ordinary pollination may occur, the author asserts that the embryo is 
usually formed without any process of fertilisation, arising as an out- 
growth of the embryo-sac. The full development of both the male 
and female flowers appears to depend on a simple hypertrophy of 
the tissues of the fig, resulting from the irritation caused by the 
female insect in the act of laying its eggs within the ovary of the 
‘« vall-flowers’” of the male figs, and of their persistent attempts to do 
the same within the flowers of the female figs, in which attempts 
they are frustrated by the great thickness of the wall of the ovary. 
In connection with the fertilisation of the fig, it may be mentioned 
that Professor Riley has enumerated fourteen species of insect as 
taking part in the so-called “‘ caprification”’ of the wild figs of North 
America. He recommends to the fig-growers of California the intro- 
duction for this purpose of Blastophaga psenes. 
With regard to the connection between the duration of life of the 
individual and the mode of fertilisation, Meehan makes the general 
statement that flowers which are wholly dependent on insects for 
their fertilisation are always perennials, and that an innumerable 
number of their flowers fall unfertilised; while all annuals, on the 
other hand, can self-pollinate themselves when cross-pollination fails ; 
and in almost all cases all the flowers of annuals are fertile. 
The phenomena of hybridity in the vegetable closely resembles 
those in the animal kingdom. It is possible to fertilise an ovule by 
pollen belonging to a different species, but only if the two species are 
very nearly allied. It is very rarely that species which are fertile 
with one another can be placed in different genera. Hybridisation is 
one of the every-day resources of the gardener; but that cross- 
breeding occurs in nature has been doubted by some. There seems, 
however, scarcely to be room for doubt that in some of our abundant 
wild genera, such as Rubus, Salix, and Hieracium, hybridity is not un- 
common in nature. It has long been known that in some genera, such 
as Passiflova, and in some Orchidez, the ovules appear to be even 
more readily fertilised by pollen of a different species. W. Focke 
now states that this is also the case with the species of Lilium belonging 
to the group bulbiferum, and with some species of Hemerocallis; and 
J. H. Wilson affirms the same respecting the Cape genus A/buca, also 
belonging to the Liliacee. According to Millardet none of the 
so-called hybrid vines cultivated in Europe are true hybrids, 7.e., 
products of the crossing of distinct species; they all spring from the 
crossing of different races of the same species, Vitis vinifera. He 
further states that, in the vine, it is the male parent that exercises the 
preponderating influence on the descendants. Rimpau has carried 
out a series of experiments on the crossing of some of our most 
common agricultural plants. He has obtained ten artificial and nine 
natural hybrids in wheat, and also obtained a fertile hybrid between 
