370 ANGIOSPERMAE—DICOTYLEDONES 



786. Phyllanthus L. 



2543- P. Niruri L. (?) (Ludwig, Kosmos, Leipzig, i, 1872.) — This species is 

 indigenous to Brazil. At the base of the inflorescence are situated smaller whitish- 

 green, bell-shaped male flowers provided with nectaries, and above them the larger 

 green female ones with longer stalks, devoid of nectar. Anthesis begins by the 

 almost simultaneous opening of the male and female flowers situated in the lowest 

 part of the inflorescence. 



Visitors. — Ludwig and Herm. Miiller supposed these to be small Diptera. 



787. Mercurialis L. 



Flowers anemophilous ; dioecious, rarely monoecious, still more rarely tri- 

 monoecious. 



2544. M. annua L. (F. Heyer, Inaug.-Diss., Halle, 1883.) — Heyer says that 

 the ratio of male to female plants in this species is as 105-86 : 100 (on the average 

 calculated from 21,000 specimens). Monoecism occurs sometimes, single male 

 flowers appearing on the female plants, or conversely. Pollen is transferred from 

 one plant to another by the wind. 



The development of germinable seeds without fertilization, i. e. partheno- 

 genetically, has already been described in Vol. I, p. 61.' 



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

 stated. — 



MacLeod (Flanders), 2 hover-flies (Bot. Jaarb. Dodonaea, Ghent, vi, 1894, 

 p. 252). Plateau (Flanders), a Dermestid beetle (Anthrenus verbasci L., freq., 

 po-dvg.), Thrips, a moth (Botys sp.), and 4 hover-flies — i. Syritta pipiens Z. ; 

 2. Syrphus corollae L. ; 3. Eristalis tenax L. ; 4. E. arbustorum L. 



2545. M. perennis L. (Thomas, Bot-. Centralbl., Cassel, xv, 1883, p. 29 ; 

 J. Saunders, J. Bot., London, xxi, 1883, pp. 181-2 ; Warnstorf, Schr. natw. Ver., 

 Wernigerode, xi, 1896.) — Thomas describes this species as dioecious, and occasion- 

 ally monoecious, while Saunders states that it is also sometimes trioecious. Warn- 

 storf describes the male flowers as arranged in clusters of 4 to 7, grouped in 

 pseudo-spikes of which the apical flower opens first. The two globular, yellow 

 anthers, situated upon pale delicate filaments, diverge and dehisce upwards. The 

 anther-lobes become indigo-blue in colour after the pollen-grains are scattered. 

 These are sulphur-yellow in colour, closely tuberculate, ellipsoidal, on an average 

 37 /x long and 20 /x broad. Kemer says that the stigmas of the female flowers are 

 receptive at least two days before the anthers of the male ones dehisce (' Nat. Hist. 

 PI.,' Eng. Ed. I, II, p. 403). 



' Juel (Vet.-Ak. Handl., Stockholm, xxxiii, 1900) says that in this species there is no real 

 parthenogenesis (i. e. the development of a new individual from a cell which is morphologically an 

 unfertilized egg-cell), but only seed-formation without previous fertilization. This also applies to 

 Caelebogyne ilicifolia, /. Sm. (vol. i, p. 60), some species of Alchemilla (Murbeck, Bot. Not., 

 Lund, 1897, p. 273), as well as to the plants of Antennaria alpina in the Innsbruck Botanic 

 Garden, which are described by Kemer as parthenogenetic. Juel (op. cit) proves by his investiga- 

 tions on the embryology of this plant that ' Kemer's hitherto unproved assertion of parthenogenesis 

 in Antennaria alpina is nevertheless true." 



