ADAPTATIONS FOR CLOSE FERTILIZATION. "241 



434. Cleistogamy. Here the intention and the accomplishment 

 of self-fertilization are unmistakable. This peculiar dimorphism 

 consists in the production of very small or inconspicuous and 

 closed flowers, necessarily self-fertilized and fully fertile, in 

 addition to ordinary, conspicuous, and much less fertile, though 

 perfect flowers. Two cases were known to Linnaeus, 1 and one 

 of them to Dillenius before him ; those of Viola have long been 

 familiar in the acaulescent species ; Adrien Jussieu made out 

 the structure of the cleistogamous flowers in certain Malpighiaceae 

 in 1832, and recorded in 1843 that Adolphe Brongniart had well 

 investigated those of Specularia, and that Weddel had discov- 

 ered them in Impatiens Nolitangere. A full account of the then 

 known cases was given by Mohl ' 2 in 1863 ; but D. Mueller, of 

 Upsala, who examined Viola canina, is said by Darwin to have 

 given, 3 in 1857, "the first full and satisfactory account of any 

 cleistogamic flower." The appropriate name of cleistogamous 

 was given by Kuhn, 4 in 1867, and is now in common use. 



435. Cleistogamous flowers are now known in about 60 genera, 

 of between twenty and thirty natural orders, of very various 

 relationship, though all but five are Dicotyledons. All but the 

 Grasses 5 and Juncus are entomophilous as to the ordinary 

 flowers, and most of these such as have special arrangements for 

 their intercrossing, either by dichogamy, heterogone dimorphism 

 or trimorphism (in Oxalis) , or such special contrivances as those 

 of Orchids. 



436. It has been said that the ordinary flowers in such plants 

 are sterile, and perhaps they always are so except when cross- 

 fertilized : in most cases they are habitually infertile or spar- 

 ingly fertile. Probably they suffice to secure in every few 

 generations such benefit as a cross may give, while the principal 



1 Campanula (now Specularia) perfoliata and Ruellia clandestina, the 

 latter a cleistogamous state of R. tuberosa. Linnaeus did not make out the 

 structure of the flowers, but supposed them to want the stamens. 



2 In Bot. Zeitung, xxi. 309. 



3 In Bot. Zeitung, xvi. 730. 



* Ibid. xxv. 65. The name (denoting "closed up "union or fertilization) has 

 been written deistogenous, which is not so proper. We prefer dei'slot/amou* to 

 cleistogamic (and so of similar terms), as best harmonizing with tin- Latin 

 adjective form, both in form of termination and in euphoniously taking tin- 

 accent upon the antepenult. 



5 Amphicarpum (Milium amphicarpon, Pursh) is the earliest recognized 

 cleistogamous Grass, except perhaps Leersia oryzoides. Some species of 

 Sporobolus are like the latter, and Mr. C. G. Pringle has recently detected 

 such flowers concealed at the base of the sheaths in Danthonia. Amer. 

 Jour. Sci. January, 1878, 71. 



16 



