1903] Biological NOTES ON Canadian SPECIES OF Viola. 151 



besides that it bears a spur of variable lenj^^th. The five stamens 

 are closely applied to the ovary ; they have short filaments, and 

 at their summit generally a membranaceous appendage formed by 

 the prolongrttion ol the connective ; the two anterior stamens are 

 provided with a spur-like nectary, which protrudes a consideiable 

 distance into the petaloid spur ; this nectary shows several modi- 

 fications in North American species and ought to be studied and 

 described in the diagnoses. Finally, the ovary has a club shaped 

 style and bears the stigma in a groove on the anterior side. 



These peifect flowers are, however, far from being always 

 fertile, and it appears, from our own observations, as if they are 

 sterile in a number of the acaulescent, purple-flowered species, at 

 least in the vicinity of Washington, but whether these same 

 species behave in the same way further north would be worth 

 while determining. The other kind of flower, the cleistogamic, 

 is often, but very incorrectly described as "apetalous," evidently 

 from the fact that it has not hitherto been carefully examined in 

 this country. The term "cleistogamic" is thus designated to 

 such flowers as remain closed, in which the petals are merely 

 present as rudiments or, sometimes, totally absent, and in which 

 the stamens are reduced in number, besides that their anthers 

 are small and contain but a few pollen-grains, which generally 

 emit iheir tubes while still enclosed in the anther-cell. The pistil 

 is in these flowers smaller than in the perfect ones, and the stigma 

 is often scarcely developed. These flowers nevertheless produce 

 a larger quantity of seeds than the perfect, and they have, in a 

 number of cases, the power of burying themselves in ihe ground,, 

 where the seeds thus become ripened, or they are borne on erect, 

 aerial pedunck-- like the perfect flowers. 



Cleistogamic flowers are known from very nearly sixty genera, 

 especially among the Papilionacece, AcanthacecB, MalpighiacecE, in 

 certain species of Ojca/w, Lamium, Linaria, Drosera, Viola, etc., 

 while they are rare among the Monocotyledones : /uncus, Hordeum^ 

 Leersia, Aynphicarpiim, Commelina, etc.* 



In the genus Viola these flowers were known already to 

 Dillenius and Linnaeus, which is readily to be seen from their 



1 Compare Darwin : Different forms ol flowers, p. 310. 



