236 ANGIOSPERMAEDICOTYLEDONES 



can scarcely be said to exist. The pollen-grains are not homogamous. As the 

 shorter stamens grow more rapidly than the style, the stigmas are often seen to 

 be covered with pollen, but this apparently does not lead to autocarpy. Nicotra 

 also observed cleistogamous flowers, or at least transition-forms towards such, and 

 these perhaps now and then set fruits. 



4. Tribe Balsamineae. 



176. Impatiens L. 



Markedly protandrous bee flowers, or more rarely hover-fly flowers. The nectar 

 is secreted in the end of the calyx-spur. Some species (including I. Noli-tangere), 

 especially North American ones, occasionally possess cleistogamous flowers, according 

 to Hugo von Mohl (Bot. Ztg., Leipzig, xxi, 1863). Von Mold's description of these 

 is given in Vol. I, pp. 52-3. Some North American species of the genus are visited 

 by humming-birds. 



599. I. Noli-tangere L. (Kirchner, 'Flora v. Stuttgart,' pp. 346-7; Knuth, 

 'Grundriss d. Bliitenbiol.,' pp. 38-9, 'Bloemenbiol. Bijdragen.') In the large 

 pendulous flowers of this species, which are golden-yellow, dotted with red in the 

 throat, the united anthers of the five stamens are situated on the upper lip, and 

 surround the stigma. When the flower opens, the anthers have dehisced, so that 

 a humble-bee after getting at the nectar must carry away pollen on its back. 

 At a later stage the stamens separate and the stigma matures, assuming the position 

 previously occupied by the anthers. Automatic self-pollination, by pollen that 

 remains clinging to the anthers, is possible. 



Visitors. I saw at Eutin two species of humble-bee skg., Bombus lapidarius Z. 

 $ and 5, and B. hortorum Z. 5 and S (also the variety nigricans Schmiedekn.). 



1 further noticed a wasp Vespa media Retz. 5 at work on the flowers, and it 

 seemed to reach the deeply concealed nectar. At Flensburg I also saw a humble- 

 bee Bombus terrester Z. which, however, was unable to completely empty the 

 spur. In Central Germany, Herm. Miiller also saw humble-bees, without being able, 

 however, to determine their species. Loew noticed a small bee, Halictus cylindricus 

 F. 5, po-cltg., and, at the same time, incidentally effecting cross-pollination. As 

 unbidden guests, Herm. Miiller observed a species of Halictus (H. zonulus Sm. 5), 



2 beetles (Meligethes and Dasytes flavipes F.), and a fly (Sargus cuprarius Z. S). 



Hermann Miiller (' Alpenblumen,' p. 179) found the flowers in Prattigau 

 frequently perforated by Bombus mastrucatus Gerst., and remarks that the flower 

 there probably often has recourse to automatic self-pollination, its capacity for which 

 was demonstrated by Darwin ('Cross- and Self-Fertlsn.,' p. 367). 



600. I. parviflora DC. (Bennett, ' On the Floral Structure of Impatiens fulva 

 AW/.' ; Henslow, ' On the Self-fertilisation of Plants ' ; Knuth, ' Bloemenbiol. Bij- 

 dragen.') The small, bright yellow flowers of this plant possess the same flower 

 mechanism as the last species, but, according to Henslow, automatic self-pollination 

 is favoured. Bennett states that cleistogamous flowers do not occur. 







