Ueber Blumen und Insecten. 



fully admitted, in the Bulletin of the Torrey Botanical Club, that this species is 

 truly heterostyled and trimorphic. The last point on which I wish to remark is 

 the difference between the males and females of certain butterflies in the neuration 

 of the wings, and in the presence of tufts of peculiarly-formed scales. An American 

 naturalist has recently advanced this case as one that cannot possibly be accounted 

 for by sexual selection. Consequently, Fritz Miiller's observations which have 

 been published in full in a recent number of Kosmos, are to me highly interesting, 

 and in themselves highly remarkable. 



Down, Beckenham, Kent, November 21. Ch. Darwin. 



You mention ("Different Forms of Flowers," page 331), the deficiency of 

 glands on the calyx of the cleistogamic flowers of several Malpighiaceae, sug- 

 gesting, in accordance with Kerner's views, that this deficiency may be accounted 

 for by the cleistogamic flowers not requiring any protection from crawling insects. 

 Now I have some doubt whether the glands of the calyx of the Malpighiaceae 

 serve at all as a protection. At least, in the one species, the fertilisation of which 

 I have very often witnessed, they do not. This species, Bunchosia Gaudichaudiana, 

 is regularly visited by several bees belonging to the genera Tetrapedia and Epi- 

 charis. These bees sit down on the flowers gnawing the glands on the outside 

 of the calyx, and in doing so the under side of their body is dusted with pollen, 

 by which, afterwards, others flowers are fertilised. 



There are here some species of Solanum (for instance .S. palinacanthiim] 

 bearing on the same plant long-styled and short styled flowers. The short-styled 

 have papillae on the stigma and apparently normal ovules in the ovary, but not- 

 withstanding they are male in function, for they are exclusively visited by pollen- 

 gathering bees (Melipona, Euglossa, Augochlora, Megacilissa, Eophila, n. g., and 

 others), and these would probably never insert their proboscis between the 

 stamens. 



In a few months I hope to be able to send you seeds of our white-flowered 

 violet with subterranean cleistogamic flowers. I was surprised at finding that on 

 the Serra (about uoo metres above the sea) this violet produced abundant normal 

 fruits as well as subterranean ones, while at the foot of de Serra, though it had 

 flowered profusely, I could not find a singe normal fruit, and subterranean ones 

 were extremely scarce. 



According to Delpino the changing colours of certain flowers would serve 

 to show to the visiting insects the proper moment for effecting the fertilisation 

 of these flowers. We have here a Lantana the flowers of which last three days, 

 being yellow on the first, orange on the second, purple on the third day. This 

 plant is visited by various butterflies. As far as I have sean the purple flowers 

 are never touched. Some species inserted their proposcis both into yellow and 

 into orange flowers (Danais eripptis, Pieris aripa), others, as far as I have 

 hitherto observed, exclusively into the yellow flowers of the first day (Heliconius 

 apseudes, Colcenis Julia, Eurema leuce). This is, I think, a rather interesting 

 case. If the flowers fell off at the end of the first day the inflorescence would 

 be much les conspicuous; if they did not change their colour much time would 

 be lost by the butterflies inserting their proboscis in already fertilised flowers. 



Fritz M tillers gesammelte Schriften. 37 



