ALISMACEAE 505 



Jordan points out turther that the three petals form an alighting-platform, from 

 which the entrance leads between the stamens to the middle of the flower. Warnstorf 

 describes the pollen-grains as saffron-yellow in colour, biscuit-shaped, closely tuber- 

 culate, about 25 /i broad and up to 37-5 /x long. 



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

 stated. — 



Harm. Miiller, the fossorial wasp Gorytes fargei Schuck. { = G. campestris Z.) 

 $, skg. Knuth ('Bl. u. Insekt. a. d. nordfr. Ins.,' p. 167), 3 hover-flies, several bees, 

 and 2 Lepidoptera. Heinsius (Holland). — A. Diptera. (a) Empidae: i. Empis 

 livida Z. S. (b) Muscidae : 2. Anthomyia sp. S ; 3. Onesia floralis /?.-Z>. J ; 4. Pyrellia 

 cadaverina Z. $ ; 5. Scatophaga stercoraria Z. 5. B. Hymenoptera. (a) Apidae : 

 6. Halictus leucopus K.<^. (h) Sphegidae: 7. Crabro cribrarius Z.J and $ (Bot. 

 Jaarb. Dodonaea, Ghent, iv, 1892, p. 68). H. de Vries (Netherlands), 2 humble- 

 bees — Bombus subterraneus Z. 5, and B. terrester Z. S (Ned. Kruidk. Arch., 

 Nijmegen, 2. Sen, 2. Deel, 1875). MacLeod (Flanders), 2 hover-flies (Bot. Jaarb. 

 Dodonaea, Ghent, v, 1893, p. 291). Schiner (Austria, teste Egger), the hover-fly 

 Melithreptus formosus Egg. 



CXXIII. ORDER NAIADACEAE LINK. 

 962. Naias L. 



Flowers monoecious or dioecious and adapted for pollination by water. The 

 pollen-grains possess no extine, are globular or ellipsoido-cylindrical in the closed 

 anther, and tube-shaped when examined in water. 



2944. N. major All. (Magnus, ' Sur les ph^nom. de la poOin. dans les pi. du 

 gen Najas ' ; Jonsson, ' Om Befrukt. hos Slagtet Najas, etc' ; Kerner, ' Nat. Hist. PL,' 

 Eng. Ed. I, II, p. 105.) — The flowers of this species are dioecious. The male 

 blossom consists of one stamen only, bearing a terminal four-lobed anther, and 

 surrounded by a two-layered, closed involucre, the outer layer produced into a toothed 

 beak, while the inner is united to the wall of the anther almost to the tip. This inner 

 layer splits into four lobes which roll backwards, and the pollen then escapes into the 

 water. Jonsson states that the pollen-grains, owing to the large number of starch- 

 grains which they contain, are heavier than water, and so sink down and are caught 

 by the stigmas of the female-flowers, which consist only of an ovary with 2-3 stigmatic 

 branches. Magnus says that the pollen-grains have already developed tubes in the 

 dehisced anther. 



2945. N. flexilis Rostk. et Schmidt ( = Caulinia flexilis Willd.). (Jonsson, 

 op. cit. ; Magnus, op. cit.) — The flowers of this species are monoecious. The male 

 blossoms, according to Jonsson, are situated higher on the plant and are more 

 numerous than the female ones. The inner involucral layer of the former, united to 

 the wall of the anther, splits into two valves. The female flower bears two stigmatic 

 branches and two spiny ones. 



963. Scheuchzeria L. 



Flowers probably anemophilous and protogynous. 



2946. S. palustris L. (Buchenau, in Engler's ' Pflanzenreich,' Leipzig, Heft 

 16.) — The dull-brownish green perianth leaves of flowers belonging to this species 



