. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. 366 ANGIOSPERMAE—DICOTYLEDONES. Fig. h6i. Euphorbia, L. (from nature), (i) E. Pephts, L,, in the first (female) stage ; the stigmas project a little from the involucre. (2) E. Helioscopia, L., in the second (male) stage; the ovary (the female flower) with its non-receptive stigmas hangs far out on a curved stalk: the stamens (mate flowers) protrude from the in- volucre. branchlet. This is composed of several (10-12) male flowers (each consisting of a single-
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. 366 ANGIOSPERMAE—DICOTYLEDONES. Fig. h6i. Euphorbia, L. (from nature), (i) E. Pephts, L,, in the first (female) stage ; the stigmas project a little from the involucre. (2) E. Helioscopia, L., in the second (male) stage; the ovary (the female flower) with its non-receptive stigmas hangs far out on a curved stalk: the stamens (mate flowers) protrude from the in- volucre. branchlet. This is composed of several (10-12) male flowers (each consisting of a single-stalke(J stamen) with a central female flower, and is surrounded by a calyciform involucre with a four- to five-lobed limb. g The glands of this investment secrete a shallow layer of completely exposed nectar. This inflorescence, oecologically equiva- lent to a single flower, is strongly proto- gynous {cf. E. palustris Z.). The three bilobed stigmas emerge first from the in- volucre, and may be dusted with foreign pollen if insects visit the flowers. Later, when the ovary (on a long, curved stem) projects far beyond the involucre, the stamens gradually elongate one after another, dehiscing at the same time, and take the place which was occupied in the first stage by the stigmas. Pollination is effected exclusively by flies, but beetles and wasps are occasional visitors, and, in places where the plants grow in large numbers close together, bees may also be observed. Kemer states that the anthers close in damp air and open again when it is dry. Jordan observed that they turn their pollen-covered sides to the flower entrances above the nectaries. 2521. E. helioscopia L.— Visitors.—The following were recorded by the observers, and for the localities stated.— Herm. Miiller, Anthomyia sp. and other flies. Knuth (' Bl. u. Insekt. a. d. nordfr. Ins.,' p. 167), 5 Diptera—(a) Muscidae : i. Anthomyia sp. (3) Syrphidae : 2. Melanostoma mellina L.; 3. Syritta pipiens L.; 4. Syrphu
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