502 ANGIOSPERMAE—MONOCOTYLEDONES 



cross-pollination, if they come from another flower, but are able, on the other hand, 

 to bring about self-pollination if they alight on a petal. Warnstorf describes the 

 pollen-grains as yellow in colour, polyhedral, on an average 25 ju, in diameter. 



Visitors. — The following were recorded by the observers, and for the localities 

 stated. — 



Herm. Miiller (H. M.) and Knuth (Kn.), 7 hover-flies, skg. and po-dvg. — 

 1. Ascia podagrica F. (H. M.), very numerous ; 2. Eristalis arbustorum L. (Kn.) ; 

 3. E. sepulcraUs L.; 4. Melanostoma mellina L. (Kn., H. M.); 5. Melithreptus 

 scriptus L. (H. M.) ; 6. Syritta pipiens L. (Kft., H. M.) ; 7. Syrphus ribesii L. 

 (Kn.). MacLeod (Flanders), a short-tongued bee, 4 hover-flies, and 5 Muscids 

 (Bot. Jaarb. Dodonaea, Ghent, v, 1893, p. 289), Scott-Elliot (Dumfriesshire), a short- 

 tongued bee, 8 hover-flies, 5 Muscids, and a Lepidopterid (' Flora of Dumfriesshire,' 

 p. 164). 



958. Echinodorus Rich. 



2940. E. ranunculoides Engelm. (= Alisma ranunculoides L.). — In 

 flowers of this species the three petals are white with a faint tinge of pink and a 

 basal yellow blotch; they are about 8 mm. long and to mm. broad at the widest 

 part; the diameter of the flower is therefore about 15 mm. As only a few such 

 flowers are united into a panicle and the secretion of nectar is small, visitors are 

 naturally rare. Automatic self-pollination is therefore ensured, the six short, vertical 

 stamens projecting beyond the stigmas, which mature simultaneously with them, 

 autogamy by fall of pollen being thus inevitable. Should insects visit the flowers, 

 however, cross-pollination is also possible. 



959. Elisma Buchen. 



2941. E. nataxis Buchen. (= Alisma natans Z., and Echinodorus natans 

 Engelm.).— Hildebrand (' D. Geschlechts-Vert. b. d. Pfl.,' p. 90) and Kerner state that 

 submerged flowers of this species fertilize themselves pseudo-cleistogamously. 



960. Sagittaria Rupp. 



Monoecious pollen-flowers (.''). 



2942. S. sagittifolia L. — The diameter of the male flowers of this species 

 was about 2 cm. in the plants which I examined near Kiel ; female flowers may be 

 at once distinguished by their smaller size. The white petals possess a brilliant red 

 nectar-guide at their base, which suggests the presence of juicy tissue. When treated 

 with Fehling's solution and orthonitrophenylpropionic acid {cf. Leucojum aestivum L.) 

 there was no deposition of colouring matter in the male flowers. 



The plants in the neighbourhood of Kiel seemed to be protogynous, for the 

 female flowers were already faded when the pollen-flowers opened. Fruits are set 

 scantily. 



Kolreuter pointed out (' Dritte Fortsetzung ') that anemophily is improbable or 

 at least very doubtful. Hildebrand (op. cit., p. 9) observed a plant of which the 

 male and female flowers were not normal. He says (Bot. Ztg., Leipzig, h, 1893) 

 that the male and female flowers are situated in separate whorls. 



Warnstorf (Verb. bot. Ver., Berlin, xxxviii, 1896) says that the lower female 



