Chap. VIII. ON CLBIST06AMIC FLOWERS. 33Y 



vital force is probably a far more efBeient 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 350; with 

 Leersia at 310 ; 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 Pffiony.* 

 We thus see that cleistogamic flowers produce seeds with 

 a wonderfully small expenditure of pollen; and they 

 produce as a general rule qirite 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 oi 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. !N'o less than eight of the genera 

 in the list at the beginning of this chapt-er include 

 species which act in this manner, namely, several 



* The anthoritiea for these stn^ments are given in my ' Effects of 

 Cross and Self-Fertilisation,' p. 376. 



