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His view that cleistogamous flowers are derived from originally chasmogamous flowers has been confirmed by more recent researches.

There are still but few researches on this point; Darwin found that in Ononis minutissima, which produces cleistogamous as well as self-fertile chasmogamous flowers, the crossed and self-fertilised capsules produced seed in the proportion of 100:65 and that the average bore the proportion 100:86.

The corolla and frequently other parts of the flower are reduced; the development of the seed may, therefore, be accomplished with a smaller expenditure of building material than in chasmogamous flowers; there is also no loss of pollen, and thus a smaller amount suffices for fertilisation.

Almost all these plants, as Darwin pointed out, have also chasmogamous flowers which render cross-fertilisation possible.

Conditions of nutrition in the broader sense are the factors which determine whether chasmogamous or cleistogamous flowers are produced, assuming, of course, that the plants in question have the power of developing both forms of flower.