1893. HYBRIDITY IN PEANTS. 207 
states that the cultivated grape-vine is also occasionally pollinated 
by honey-bees. 
As has already been pointed out, those flowers which are 
unisexual—z.e., which have either pistil and no stamens, or stamens 
and no pistil—must necessarily be cross-pollinated. Schulz, 
however, states that in many of our trees which are normally uni- 
sexual, hermaphrodite flowers do occasionally occur. Thus, in the 
elder, hermaphrodite flowers or transitional forms between these and 
unisexual are frequently to be found at the base of the male catkins. 
Hermaphrodite flowers also occur in the birch, though less frequently, 
very rarely in the hazel; in the oak there are often ovaries at the 
base of the male catkins, and rudiments of stamens in the female 
flowers. The mode of fertilisation of the hazel is involved in great 
obscurity, since scarcely a trace of the ovules can be found in the 
female flowers at the time when the catkins are discharging their 
pollen. In the ash, all kinds of condition may be met with, male, 
female, and hermaphrodite flowers ; and either the same or different 
kinds on the same tree. The ash is probably on the road to becoming 
completely dicecious. 
Few phenomena in physiology, whether animal or vegetable, are 
more puzzling than those of parthenogenesis, that is, the production of 
a normal fertile embryo without any preceding act of fertilisation. 
The example in the vegetable kingdom of Calebogyne is familiar to all 
students of text-books. Another very remarkable instance is now on 
record. There have been few more interesting contributions to 
botanical science during the last few years than Dr. D. D. Cunning- 
ham’s ‘*On the Phenomena of Fertilisation in Ficus Roxburghit,” pub- 
lished in Calcutta in 1889, with beautiful illustrations. According to 
Dr. Cunningham the figs are in this species either male or female, 
all on the same plant being of the same sex. The male figs contain 
perfect male flowers, which produce pollen, and atrophied female or 
‘‘ gall-flowers,”” which never produce seed, but within the ovaries of 
which the eggs of an insect—usually a species of Eupyistis—are de- 
posited and develop into pupae. The female figs contain perfect 
female flowers, in which the eggs of the insect are never found, and 
which produce fertile seeds. The terminal opening of both the male 
and female figs is so obstructed by a covering of bracts that they are 
almost completely closed chambers; and the perfect development of 
both the male and female flowers is dependent on the access of the 
‘* fig-insect ”’ to the interior of the cavity, without which they do not 
arrive at a functional condition. Although the development of the 
embryo in the female fig is essentially connected with the access of 
the insects to the cavity, Dr. Cunningham believes that it does not 
depend on the introduction of pollen by their agency. The nearly 
entire closure of the opening by bracts presents analmost insuperable 
obstacle to the introduction into the female fig of a sufficient quantity 
of pollen for the fertilisation of every one of the very numerous ovules 
