EUPHORBIACEAE 371 



Visitors. — Scott-Elliot (Dumfriesshire) observed the honey-bee ('Flora of 

 Dumfriesshire,' p. 152). 



2546. M. ovata Sternb. et Hoppe (= M. perennis L., according to the Index 

 Kewemis). — Kemer's remark about the last species applies to this one also. 

 A. H. W. Dod (J. Bot., London, xxxiii, 1895, p. 185) observed several male plants 

 with one or two female flowers, and one female plant with one male flower. 



Visitors. — Frey (Aargau) observed the moth Brephos puella Esp. 



XCVIII. ORDER URTICACEAE ENDL. 



788. Urtica L. 



Flowers anemophilous ; monoecious or dioecious. When they open, the fila- 

 ments, hitherto curved inwards and downwards, expand and spring out of the 

 perianth, the anthers dehiscing at the same time and scattering their pollen in a small 

 cloud. 



2547. U. urens L. (Herm. Miiller, 'Weit. Beob.,' I, pp. 294-5; Kerner, 

 'Nat. Hist. PI.,' Eng. Ed. i, II, p. 313; MacLeod, Bot. Jaarb. Dodonaea, Ghent, 

 vi, 1894, pp. 134-5.) — The female flower in this species is one mm. long and 0-5 mm. 

 broad. It consists of a green tetramerous perianth, and an ovary bearing a tuft of 

 radiating transparent stigmatic hairs. The male flower matures somewhat later than 

 the female one in the same leaf-axil, and its diameter is four times that of the latter. 

 The four stamens are superposed on the four perianth leaves, and are bent so far 

 inwards that the thick anthers lie in the base of the flower, while the inwardly curved 

 filaments are in a condition of outward tension. This increases as they elongate 

 until the resistance is finally overcome. The filaments suddenly straighten, the 

 anthers dehiscing simultaneously and scattering a cloud of pollen, thus effecting 

 crossing with adjacent stocks in which the stigmas are already receptive. 



2548. U. dioica L. — The male flowers of this species possess the same ex- 

 plosive mechanism as those of U. urens, but dioecism is the usual rule. Monoecious 

 stocks occur, however, bearing female inflorescences at the top, mixed ones in the 

 middle, and male ones at the bottom (Hildebrand). 



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

 stated. — 



Herm. Miiller, the hover-fly Syrphus arcuatus Fall. (?), po-dvg. Von Fricken 

 (Westphalia and E. Prussia) and Redtenbacher (Vienna), the Nitidulid beetle 

 Brachypterus urticae F. 



789. Parietaria L. 



Flowers anemophilous ; trioecious — there being hermaphrodite, male and female 

 flowers on the same stock. The hermaphrodite ones are protogynous. The anthers 

 possess a similar explosive mechanism to that of Urtica, for the stamens, stretched 

 Kke watch-springs at first, suddenly burst free, scattering the pollen into the air at the 

 same time. 



B b 2 



