EUPHORBIACEAE 365 



offer a small quantity of nectar to visitors, the female possessing three small, fleshy 

 nectaries close together, each secreting a small drop of nectar. These are situated 

 touching each other on the ovary, which is surrounded by five or six greenish 

 perianth leaves. In the male flowers the vestigial ovary forms the nectary, apparently 

 secreting tiny drops of nectar. The three styles in the female flowers alternate with 

 the nectaries, and project beyond them, each bearing a two-lobed stigma on its inner 

 side : no trace of anthers is to be seen. In the male flowers the four stamens project 

 far beyond the nectary, which is surrounded by the four perianth leaves. The anthers 

 are thick and cordate. 



The spikes are feebly protogynous. The stigmatic papillae of the apical flower 

 (which is sometimes absent) are receptive before the anthers of the surrounding 

 male flowers have dehisced, and the stigmas remain in that condition until all the 

 male flowers on the spikelet have shed their pollen. The apical flower can therefore 

 easily be pollinated by insect visitors with pollen from adjacent male ones, if it has 

 not already been dusted with that of others belonging to the same or another plant. 

 Visitor.s, however, usually fly to the middle of the spikelet, which affords the most 

 convenient alighting-platform, and therefore on to the female flower, so that even in 

 the homogamous stage of the spikelet crossing with separate stocks is generally 

 effected. 



Warnstorf describes the pollen-grains as whitish in colour, spheroidal, rendered 

 opaque by low, crowded tubercles, on an average 37 yw. in diameter. 



Kerner places the box among those anemophiious species which — like most 

 ashes, the mock-privet (Phillyrea), and the pistachio (Pistacia) — bear short, thick 

 filaments and comparatively large anthers filled with mealy pollen, although he has 

 expressly stated that the male as well as the female flowers possess three central 

 nectaries each secreting a drop of nectar. 



Visitors. — The following were observed by Herm. Miiller (H. M.) and Knuth 

 (Kn.).- 



A. Diptera. {a) Muscidae -. all skg. : i. Calliphora vomitoria L. (Kn.) ; 

 2. Musca corvina F. (H. M.); 3. M. domestica L. (Kn., H. M.). (b) Syrphidae : 

 4. Syritta pipiens L., skg. or po-dvg. (H. M.) ; 5. Syrphus pyrastri Z., do. (H. M.). 

 B. Hymenoptera. Apidae : 6. Apis mellifica L. j (Kn., H. M.), po-cltg. Herm. 

 MuUer describes the behaviour of the honey-bee as follows : ' It frees the pollen from 

 the still undehisced anthers with its mandibles, regurgitates some honey from its 

 slightly protruded proboscis, and then transfers the pollen by means of the front and 

 mid legs to the hind ones. All this, however, is done so quickly that the individual 

 acts can scarcely be followed.' 



783. Euphorbia L. 



Literature. — Delpino, 'Ult. oss.,' I, pp. 157-61 ; Herm. Miiller, ' Weit. Beob.,' 

 II, p. 2 1 5 ; Kirchner, ' Flora v. Stuttgart,' p. 365 ; Kerner, ' Nat. Hist. PL,' Eng. Ed. i , 

 II, pp. 124, 173, 313 ; MacLeod, Bot. Jaarb. Dodonaea, Ghent, vi, 1894, pp. 249-50 ; 

 Knuth, ' Bl. u. Insekt. a. d. nordfr. Ins.,' pp. 130-1, ' Grundriss d. Bliitenbiol.,' 

 pp. 90-1. 



All our native spurges possess the same flower mechanism. The stem at first 

 divides into a pentamerous cyme, the rays subdividing into branches with bifurcated 

 branchlets. An inflorescence resembling a single flower is situated at the end of each 



