. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. I20 INTRODUCTION. Fig. 2g. Sympkoricarpos racemosus^ a Wasp Flower. flower was visited very eagerly by wasps at the beginning of its floral period, while later on honey-bees and humble-bees were the principal visitors. Robertson made a similar observation in Illinois, but he found that at the end of August and beginning of September, when the flowers were beginning to get scarce, wasps once more appeared as their only visitors. He concludes as follow
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. I20 INTRODUCTION. Fig. 2g. Sympkoricarpos racemosus^ a Wasp Flower. flower was visited very eagerly by wasps at the beginning of its floral period, while later on honey-bees and humble-bees were the principal visitors. Robertson made a similar observation in Illinois, but he found that at the end of August and beginning of September, when the flowers were beginning to get scarce, wasps once more appeared as their only visitors. He concludes as follows:—'This seems to be significant, for when any flower becomes reduced in numbers, its proper visitors are apt to be the last to leave it' (Trans. Acad. Sci., St. Louis, Mo., v, 1891). I have called attention ('Blutenbesucher,' I, p. 17) to the fact that the yellow anthers and brownish corolla of Scrophularia harmonize in a remarkable way with the colours of the insect visitors. A wasp with head inserted in the opening of the flower (which is precisely adapted to it) and projecting abdomen looks almost as if it were a part of the flower, so far as colour is concerned. The flowers of Lonicera alpigena are coloured in a similar way to those of Scrophularia nodosa and S. aquatica (see Fig. 31). According to Hermann Miiller's account ('Alpenblumen,' pp. 395 and 396) the flower-bud is reddish-brown. When the flower opens this colour is replaced for a short time by the dirty yellowish-white of the inner surface, while in the older flower this assumes the reddish-brown colour pos- sessed by the outer surface. It consequently follows that the groups of flowers, taken collectively, exhibit the reddish-brown colour that is elsewhere uncommon, but resembles that which we find in Scrophularia. About I mm. above its base the corolla secretes nectar very abundantly, in a ventricose ex- pansion, which is exactly wide enough to receive the head of a wasp or humble-bee. Hermann Miiller observe
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