CHAP. VIII. ON CLEISTOGAMIC FLOWERS. 337 



vital force is probably a far more efficient motive power. 

 The whole flower is much reduced in size: but what is 

 much more important, an extremely small quantity of 

 pollen has to be formed, as none is lost through the 

 action of insects or the weather; and pollen contains 

 much nitrogen and phosphorus. Von Mohl estimated 

 that a single cleistogamic anther-cell of Oxalis aceto- 

 sella contained from one to two dozen pollen-grains ; we 

 will say 20, and if so the whole flower can have produced 

 at most 400 grains; with Impatiens the whole number 

 may be estimated in the same manner at 250; with 

 Leersia at 210 ; and with Viola nana at only 100. These 

 figures are wonderfully low compared with the 243,600 

 pollen-grains produced by a flower of Leontodon, the 

 4,863 by an Hibiscus, or the 3,654,000 by a Paeony.* 

 We thus see that cleistogamic flowers produce seeds with 

 a wonderfully small expenditure of pollen; and they 

 produce as a general rule quite as many seeds as the 

 perfect flowers. 



That the production of a large number of seeds is 

 necessary or beneficial to many plants needs no evi- 

 dence. So of course is their preservation before they 

 are ready for germination; and it is one of the many 

 remarkable peculiarities of the plants which bear 

 cleistogamic flowers, that an incomparably larger pro- 

 portion of them than of ordinary plants bury their 

 young ovaries in the ground; an action which it 

 may be presumed serves to protect them -from being 

 devoured by birds or other enemies. But this advan- 

 tage is accompanied by the loss of the power of wide 

 dissemination. !S!"o less than eight of the genera 

 in the list at the beginning of this chapter include 

 species which act in this manner, namely, several 



* The an tli ori ties for these statements are given in my ' Effects of 

 Cross and Self-Fertilisation,' p. 376. 



