2o6 NATURAL SCIENCE. March, 



but throughout the later spring and summer very inconspicuous 

 flowers are abundantly produced, completely concealed in their cal3'x, 

 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 Leguminosae 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 Oxalis, 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 mantimum , Scleranthus anmms, &c. In Polygonum 

 acre and Hydvopiper 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 Myrmecodia, 

 one of the genera which furnish abodes in their stems for colonies of 

 ants ; and he suggests the explanation that the flovv^ers were at hrst 

 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 Vitis 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 vinifcra, and have only 

 hermaphrodite flowers, the filaments are long and erect, as in 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 



