APOCYNACEAE 89 



disagreeable odour. In other respects their mechanism agrees with that of A. andro- 

 saemifolium. In correlation with the duller colouring we find that the only visitors 

 are flies, among which large numbers of the smaller Syrphids and Muscids are im- 

 prisoned by the clips. 



Ludwig (Kosmos, Stuttgart, viii, 1881) observed that 56 flowers caught and 

 killed 88 small Muscids and Syrphids between early morning and 3 p.m. 



Visitors. Vide supra. 



1868. A. venetum L. This species is doubtfully arachnophilous {cf. Vince- 

 toxicum officinale, p. 90). 



566. Lyonsia R. Br. 



According to Loew (Bot. Centralbl., Cassel, xxviii, 1886), the flower mechanism 

 resembles that of Apocynum androsaemifolium. Schumann (op. cit.) noticed that 

 flies were killed by the flowers of species of this genus. 



567. Nerium L. 



Homogamous Lepidopterid flowers. 



1869. N. odorum Ait. (Ludwig, Bot. Centralbl., Cassel, viii, i88r, pp. 185-8.) 

 The large fragrant flowers of this species possess a large funnel-shaped corolla, 

 which becomes rotate above, and is provided with an incised corona. There are 

 nectar-guides in the form of dark-red streaks converging to the nectar-containing 

 "base of the flower. As in Apocynum the corolla-tube encloses a cone of anthers 

 covered externally by woody plates, and fused internally with the dilated end of the 

 tyle to form a pollen-chamber, beneath which is the stigmatic surface. The anther- 

 plates are produced into points below, and covered with hairs dorsally. Each stamen 

 is drawn out into a long terminal appendage, which is filiform at its base and then 

 becomes broader and feather-like. These five appendages are twisted together into 

 a loose, woolly, whitish ball, 8-9 mm. long and 4 mm. broad, which (with the corona) 

 blocks the entrance of the flower in such a way that only long-tongued Lepidoptera 

 are able to penetrate to the nectar. 



Within the flowers Lepidoptera have to overcome the same difficulties as those 

 presented by Apocynum to pollinating agents. Their proboscis can only reach 

 to the base of the flower (about 10 mm. deep) by being inserted into the narrow 

 glabrous fissures between the stamens, and has to be withdrawn between the anthers, 

 through a cleft which narrows above. In the latter operation the stigma is first 

 touched, and gets pollinated if another flower has previously been visited, after 

 which the proboscis is smeared with the viscid secretion of the upper edge of 

 the stigma, and takes up fresh clumps of pollen from the pollen-chamber. All 

 visitors do not possess the necessary strength and endurance for this, so that 

 here again unbidden guests are caught and killed. The observation of two cases 

 of the kind first called the attention of Ludwig to the mechanism of oleander flowers. 



Visitors. The larger Lepidoptera, especially the hawk-moth Sphinx nerii L. 



1870. N. Oleander L. ; 1871. N. cupreum L. ; 1872. N. Grangeanum ; and 

 1873. N. Ricciardianum. Ludwig (op. cit.) says that these species possess the 

 same flower mechanism as N. odorum. 



