They dehisce properly, but do not appear to contain much pollen. Many pollen-grains were attached by short tubes to the stigmas; but many others, still adhering to the anthers, had emitted their tubes to a considerable length, without having come in contact with the stigmas. Living plants ought to be examined, as the stigmas, at least of the long-styled form, project beyond the calyx, and if visited by insects (which, however, is very improbable) might be fertilised with pollen from a perfect flower. The most singular fact about the present species is that long-styled cleistogamic flowers are produced by the long-styled plants, and mid-styled as well as short-styled cleistogamic flowers by the other two forms; so that there are three kinds of cleistogamic and three kinds of perfect flowers produced by this one species! Most of the heterostyled species of Oxalis are more or less sterile, many absolutely so, if illegitimately fertilised with their own-form pollen. It is therefore probable that the pollen of the cleistogamic flowers has been modified in power, so as to act on their own stigmas, for they yield an abundance of seeds. We may perhaps account for the cleistogamic flowers consisting of the three forms, through the principle of correlated growth, by which the cleistogamic flowers of the double violet have been rendered double.
Vandellia nummularifolia.
Dr. Kuhn has collected all the notices with respect to cleistogamic flowers in this genus, and has described from dried specimens those produced by an Abyssinian species. (8/11. 'Botanische Zeitung' 1867 page 65.) Mr. Scott sent me from Calcutta seeds of the above common Indian weed, from which many plants were successively raised during several years. The cleistogamic flowers are very small, being when fully mature under 1/20 of an inch (1.27 millimetres) in length. The calyx does not open, and within it the delicate transparent corolla remains closely folded over the ovarium. There are only two anthers instead of the normal number of four, and their filaments adhere to the corolla. The cells of the anthers diverge much at their lower ends and are only 5/700 of an inch (.181 millimetres) in their longer diameter. They contain but few pollen-grains, and these emit their tubes whilst still within the anther. The pistil is very short, and is surmounted by a bilobed stigma. As the ovary grows the two anthers together with the shrivelled corolla, all attached by the dried pollen-tubes to the stigma, are torn off and carried upwards in the shape of a little cap. The perfect flowers generally appear before the cleistogamic, but sometimes simultaneously with them. During one season a large number of plants produced no perfect flowers. It has been asserted that the latter never yield capsules; but this is a mistake, as they do so even when insects are excluded. Fifteen capsules from cleistogamic flowers on plants growing under favourable conditions contained on an average 64.2 seeds, with a maximum of 87; whilst 20 capsules from plants growing much crowded yielded an average of only 48. Sixteen capsules from perfect flowers artificially crossed with pollen from another plant contained on an average 93 seeds, with a maximum of 137. Thirteen capsules from self-fertilised perfect flowers gave an average of 62 seeds, with a maximum of 135. Therefore the capsules from the cleistogamic flowers contained fewer seeds than those from perfect flowers when cross-fertilised, and slightly more than those from perfect flowers self-fertilised.
Dr. Kuhn believes that the Abyssinian V. sessiflora does not differ specifically from the foregoing species. But its cleistogamic flowers apparently include four anthers instead of two as above described. The plants, moreover, of V. sessiflora produce subterranean runners which yield capsules; and I never saw a trace of such runners in V. nummularifolia, although many plants were cultivated.
Linaria spuria.
Michalet says that short, thin, twisted branches are developed from the buds in the axils of the lower leaves, and that these bury themselves in the ground. (8/12.