244 ANGIOSPERMAE—DICOTYLEDONES 



XXVII. ORDER ILICINEAE DC. 

 i8i. Ilex L. 



Flowers white, often dioecious, with exposed nectar secreted in their bases. 



608. I. Aquifolium L. — This species is described by Vaucher and Darwin 

 as dioecious, but A. Schulz found that cultivated plants bore normal hermaphrodite 

 flowers which set fruits. 



MacLeod describes Belgian plants as dioecious (Bot. Jaarb. Dodonaea, Ghent, 

 vi, 1894, pp. 246-7). The male flowers possess a vestigial pistil. The anthers 

 dehisce when the flower opens. The female flowers have a much larger ovary, 

 green in colour. In both forms there is but very scanty secretion of nectar. 



Visitors. — H. de Vries observed Apis mellifica L. 5, very freq. 



XXVIII. ORDER CELASTRINEAE R. BR. 



Flowers hermaphrodite or unisexual; mostly inconspicuous, with exposed or 

 half-concealed nectar. 



182. Euonymus Toum. 



Inconspicuous protandrous flowers, with exposed nectar secreted by a fleshy 

 disk surrounding the style. 



609. E. europaeus L. (Delpino, 'Altri appar. dicog. recent, oss.,' p. 52; 

 Herm. Miiller, 'Fertilisation,' pp. 162-3; Kirchner, 'Flora v. Stuttgart,' p. 357; 

 Schulz, 'Beitr'age,' II, p. 61; Knuth, ' Bloemenbiol. Bijdragen.') — The nectar is 

 spread out in such a thin layer in the green trioecious flowers of this species, and 

 is so readily accessible that it is chiefly sought for by short-tongued insects. The 

 hermaphrodite flowers are protandrous. The four stamens are remote from the 

 stigma, and their filaments are stifi". The anthers dehisce extrorsely, while the stigma 

 is still immature. This unfolds its lobes only several days later, closing them when 

 fertilization has been effected. Automatic self-pollination is therefore entirely excluded 

 (but vide infra). When insects visit the flowers cross-pollination almost always takes 

 place. Self-pollination may occur if there have been no insect-visits in the first 

 days of anthesis. Warnstorf describes the pollen-grains as white, ellipsoidal, markedly 

 tuberculated, up to 50 /x long and 25 ju. broad. In addition to the hermaphrodite 

 flowers, unisexual ones also occur, in which non-functional vestiges of the opposite 

 sex-organs are present. According to Schulz, they are distributed gynomonoeciously 

 and andromonoeciously, rarely gynodioeciously and androdioeciously. 



Visitors. — Schulz noticed Diptera, ichneumon-flies, ants, and beetles, in the South 

 Tyrol. Herm. Miiller failed to observe beetles as visitors of the dull yellow flowers 

 of Euonymus, just as he did in the case of the somewhat similarly coloured flowers of 

 Ruta. I, too, have never seen beetles. In North and Central Germany Herm. 

 Miiller (H. M.) and myself (Kn.) have observed the following. — 



A. Diptera. (a) Bibionidae: i. Bibio hortulanus Z., skg. (H. M.) ; 2. Many 

 minute midges (H. M.). (h) Muscidae : 3. Calliphora erythrocephala Mg., skg. and 

 po-dvg. (H. M.) ; 4. C. vomitoria Z., skg. (H. M., Kn.) ; 5. Echinomyia fera Z., skg. 

 and po-dvg, (Kn.) ; 6. Lucilia cornicina F., do. (H. M., Kn.) ; 7. Musca domestica Z., 



