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254 THE FERTILISATION OF FLOWERS. [parr im. 
the closely packed flowers, to suck honey or gather pollen, come at 
once in contact with the stamens or stigmas of many flowers, and, 
as a rule accomplish cross-fertilisation by help of the proterandrous 
condition : old flowers alone, which retain some pollen upon their 
stamens when the stigmas are ripe, are liable to self-fertilisation. 
In spite of the smaller flowers and more hidden honey, this 
species can dispense with the possibility of self-fertilisation, since 
the close association of many flowers insures insect-visits and con- — 
sequent distribution of pollen more completely than is the case 
in Sedum acre. Although I only once watched the flowers of 
Sedum Telephium (August 16, 1869) in sunny weather I saw the 
following insects visit it :— 
A. Hymenoptera—(a) Apide: (1) Bombus (Apathus) campestris, Pz. ¢;_ 
(2) B. silvarum, L. 9 §, freq. ; (3) B. agrorum, F. ¢, these three sucking ; 
(4) B. lapidarius, L. $,¢.p.; (5) Halictus zonulus, Sm. 9, s. ; (b) Tenthre- 
dinide: (6) Allantus notha, Kl. (Tekl. B.). B. Diptera—Muscide : (7) _ 
Echinomyia magnicornis, Zett., s. 
Sedum atratum, L., is, according to Ricca, proterogynous with 
short-lived stigmas (665). I have found it, however, on the 
Alps to be likewise proterogynous, but liable to regular and even 
early spontaneous self-fertilisation, which is probably indispensable, 
as the plant is but little visited by insects (609). 
Sedum repens, Schleich.—This species also is proterogynous on 
the Alps, and in the absence of insects it likewise fertilises itself; 
but its flowers are rather conspicuous and more visited by insects, 
so that the need for self-fertilisation is less urgent than in the 
case of S. atratwm (600). 
THE COLOUR AND SIZE OF THE FLOWER IN CRASSULACEZ, 
The colour of the flower in Crassulaceze depends closely upon 
the adaptation of the flower to a narrow or wide circle of visitors. 
In the species of Sedum, whose honey is still quite visible and 
accessible to the most short-lipped insects, the flowers are greenish- 
yellow, yellow, or white; in Sempervivum Funkii, Braun., S. 
montanum, L., S. arachnoideum, L., and 8S. tectorwm, L., whose 
honey lies hidden, and which I have seen visited on the Alps by a 
miscellaneous company of bees, Lepidoptera, and long-tongued flies, 
the flowers are purple; in Sempervivum Wulfenii, Hopp., whose 
honey is still more concealed, the flowers, which are chiefly visited 
