206 NATURAL SCIENCE. Marcu, 
but throughout the later spring and summer very inconspicuous 
flowers are abundantly produced, completely concealed in their calyx, 
and these almost invariably give rise to fertile capsules. It would 
appear as if nature provided in them a surety for the production of 
seed in case of the continued sterility of the early spring flowers. | 
Several species of Leguminosz produce cleistogamic flowers, borne, 
in some cases, on underground shoots, the seed-vessel never appear- 
ing above the surface of the soil, and other instances are furnished 
by the genera Ovxalis, Impatiens, and many others. During the last 
few years considerable additions have been made, by Meehan and 
others, to the list of cleistogamic species, and these include several 
plants belonging to the British flora, such as Polygonum acre, Hydvo- 
piper, Persicaria, and maritiumum, Scleranthus annuus, &c. In Polygonum 
acre and Hydropiper the cleistogamic flowers are very numerous, and 
appear always to produce ripe seeds; they are small and completely 
hidden in the leaf-sheaths. W. Burck describes several species of 
tropical plants which bear flowers that never open, and must, there- 
fore, be self-pollinated, although coloured and scented, and producing 
abundance of nectar. ‘This is strikingly the case with Myvmecodia, 
one of the genera which furnish abodes in their stems for colonies of 
ants; and he suggests the explanation that the flowers were at first 
adapted for cross-pollination, but that the visits of insects have 
been gradually suspended in consequence of the attacks of the ants 
which inhabit the tubers. A. Schulz connects the appearance of 
cleistogamic flowers with unfavourable climatal conditions. In 
Tephrosia heterantha, a native of the Argentine Republic, Hieronymus 
states that the pollen-grains are few in number in the cleistogamic 
flowers, and that their tubes pierce the wall of the anthers in order to 
reach the stigma. 
The structure of the flowers in the genus /7ts is very interesting. 
In the native state all species of vine have two kinds of flower,— 
male, in which the pistil is subject to all degrees of abortion, and 
hermaphrodite, in which both stamens and pistil are fully developed. 
The stamens differ remarkably in the two kinds of flower. In the 
hermaphrodite flowers the filaments are short and curved backwards, 
so as to remove the anther as far as possible from the stigma; in the 
male they are longer and erect; but in the cultivated vines of 
Europe, all of which are varieties of Vitis vinifera, and have only 
hermaphrodite flowers, the filaments are long and erect, asin the male 
flowers of the wild plant. The pollen-grains of the two kinds of 
stamen also differ in their power of fertilisation. Millardet, who has 
given great attention to the phenomena connected with the 
fertilisation of the vine, states that in the wild state the vine 
is wind-fertilised, although the flowers have a powerful odour, the 
purpose of which is obscure. In the cultivated state he has 
observed abundance of two small coleoptera in the flowers, which 
may also probably take some part in the pollination. Kronfeld 
