6o ANGIOSPERMAE—DICOTYLEDONES 



36. Nuphar Sm. 



Flowers homogamous, or slightly protogynous, with nectar partly or completely 

 concealed, secreted by the backs of the petals, and collected in the angle between 

 sepals and petals. The sepals, which are yellow on their inner surfaces, and the 

 other floral whorls, which are of the same colour, serve to attract insects. 



ia8. N. luteum Sm. (Sprengel, 'Entd. Geh.,' p. 273; Harm. Muller, 'Ferti- 

 lisation,' p. 93; Caspary, op. cit. ; Schulz, 'Beitrage,' 11, pp. lo-ii; Kirchner, 

 'Flora V. Stuttgart,' p. 276; MacLeod, Bot. Jaarb. Dodonaea, Ghent, vi, 1894, 

 pp. 183-4; Knuth, 'Bl. u. Insekt. a. d. nordfr. Ins.,' p. 21, ' Weit. Beob.,' p. 226, 

 note I ; Axell, ' Om anord. for fanerog. vaxt. befrukt.,' p. 104 ; Warnstorf, Verh. bot. 

 Ver., Berlin, xxxvii, 1895.) — The egg-yolk yellow flowers are strongly odorous. They 

 are either homogamous or — according to Caspary and Schulz — protogynous, the 

 stigmas being fully mature at the commencement of anthesis, while the anthers 

 dehisce somewhat later in centripetal order. The stamens move towards the petals as 

 they ripen, so that automatic self-pollination is excluded. 



Warnstorf also describes the flowers as protogynous, and states that when the 

 sepals are closed the stamens are pressed together round the ovary beneath the stigma, 

 but later on, when the anthers dehisce, they bend back, so that the pollen on their 

 inner surfaces is encountered by small insect visitors. The spinose pollen-grains 

 are large, yellow, and ellipsoidal, with an average length of 63 /i, and an average 

 breadth of 37-5 /x. The spines may be as much as 8-75 ft. long. Insects creeping 

 about on the flowers efl'ect either cross- or self-polhnation. 



Visitors. — Hermann Muller (H. M.) and myself (Kn.) have observed the 

 following. — 



A. Coleoptera. {a) Chrysomelidae : i. Donacia dentata Noppe (H. M.) ; 2. D. 

 sparganii ^Ar. (Kn.) ; {b) IVi/iduh'dae : 3. Meligethes (Kn.). B. Diptera. Muscidae: 

 4. Calliphora vomitoria L. (Kn.) ; 5. Scatophaga sp. (Kn.) ; 6. Onesia florahs R.-D. 

 (H. M.). C. Neuroptera. 7. Phryganidae (Kn.). Flies and beetles have also been 

 recorded by Schulz. 



Heinsius observed in Holland numerous flies (Notiphila nigricornis Slenh., and 

 Cleigastra sp.) (Bot. Jaarb. Dodonaea, Ghent, iv, 1892, pp. 61-3). 



37. Euryale Salisb. 



129. E. ferox Salisb. — Goebel (' Pflanzenbiol. Schilder.,' II, 2, p. 363) observed 

 only submerged cleistogamous flowers on cultivated plants in the Marburg Botanic 

 Garden, while in the Munich Garden the flowers rose above the surface and unfolded 

 their bluish-violet petals. 



VII. ORDER SARRACENIACEAE ENDL. 



38. Sarracenia L. 



130. Sarracenia purpurea L. — Hildebrand states (Ber. D. bot. Ges., Berlin, 

 i, 1883) that this species is homogamous, though cross-pollination is promoted, 

 for there are recurved hooks on the stigma, which compel insect visitors to make 

 their exit to one side of the stigmatic surface. 



