GERANIACEAE 235 



sella), cleistogamous flowers have been observed. Our three native species agree 

 almost completely in their flower mechanisms. 



595. O. Acetosella L. (Herm. Muller, 'Fertilisation,' p. 159; I\IacLeod, Bot. 

 Jaarb. Dodonaea, Ghent, vi, 1894, pp. 237-8 ; Kirchner, 'Flora v. Stuttgart,' 

 pp. 342-3; Knuth, 'Grundriss d. Bliitenbiol.,' p. 39.) — Kerner states that the 

 chasmogamous flowers are open from 9 a.m. till 6 p.m. Their white petals are 

 streaked with longitudinal violet veins that serve as nectar-guides, and are also 

 marked with a yellow basal spot immediately above the nectaries. The nectar 

 collects in five depressions in the base of the corolla. These are formed by fleshy 

 appendages of the claws of the five petals, reaching as far as the filaments. The 

 length of the style being variable, the stigma may either project beyond the anthers, 

 or be situated in the middle of them. 



Hugo von Mohl (Bot. Ztg., Leipzig, xxi, 1863) was the first to describe the 

 cleistogamous flowers. (Cf. Vol. I, pp. 51-2.) 



Visitors. — These are rare. Alfken saw Apis and Bombus terrester L. 5, at 

 Bremen. 



Herm. Muller observed the following. — 



A. Coleoptera. (a) N'iliduHdae : i. Meligethes, freq. (p) Staphylinidae: 2. Oma- 

 lium florale Payk., freq. B. Thysanoptera. 3. Thrips, freq. He also noticed 

 7 Diptera, an ant, and Thrips in the Alps (' Alpenblumen,' pp. 178-9). 



In Dumfriesshire a Muscid has been recorded (Scott-Elliot, 'Flora of Dumfries- 

 shire,' p. 40). 



Burkill observed the Nitidulid Meligethes picipes Slitrm, and Thrips sp. on the 

 coast of Yorkshire (' Fertilsn. of Spring Fls.'). 



596. O. stricta' L. (Kirchner, 'Flora v. Stuttgart,' p. 343 ; Schulz, ' Beitrage,' 

 I, p. 31; Kerner, 'Nat. Hist. PI.,' Eng. Ed. i, II, p. 391.) — Kerner says that the 

 bright yeflow flowers of this species are open from 8 a.m. till 4 p.m. The flower 

 mechanism is very similar to that of the last species, but, according to Schulz, 

 the anthers of the longer stamens are at the same level as the stigma — which matures 

 simultaneously — and applied to it in such a way that automatic self-pollination is 

 inevitable. The shorter stamens serve for cross-pollination. Kerner states that 

 the flowers remain closed in bad weather. Cleistogamous flowers have not hitherto 

 been observed. 



Visitors. — MacLeod observed Apis, 2 hover-flies, and 2 Lepidoptera in Flanders 

 (Bot. Jaarb. Dodonaea, Ghent, vi, 1894, p. 238). 



597. O. corniculata L. — The flower mechanism of this species completely 

 agrees with that of O. stricta. And here too, according to Kerner, the flowers remain 

 closed in bad weather, fertilizing themselves pseudo-cleistogamously. 



598. O. cernua Thunb. — This species has been introduced into Sicily and 

 Sardinia, where, according to Nicotra (' Oss. antobiol. suU' Oxalis cernua'), it is 

 always microstylous, which explains its sterility in those islands. Stigmatic papillae 



' [In the Index Kewensi?, 0. stricta L. is given as a synonym of 0. corniculata L. — Tr.] 



