IRIDEAE 429 



dehisced when the flowers open, while the upper surface of the triangular stigmatic 

 lappets are still pressed against the stylar branches covering them. Later on, each 

 stigmatic lappet bends downwards, so that the papillose upper-side is brushed against 

 and dusted by a humble-bee creeping in ; this cannot happen in the first stage, only 

 the pollen-covered anther being then brushed against. Cross-pollination is thus 

 ensured. 



Visitors. Loew (Bredower Forest near Nauen) observed 2 humble-bees 

 Bombus variabilis Schmiedekn., and Psithyrus campestris Pz. (op. cit., p. 391) : (Berlin 

 Botanic Garden), the humble-bee Bombus hortorum Z. 5, skg. 



2682. I. germanica L. 



Visitors. Loew (Berlin Botanic Garden) observed the humble-bee Bombus 

 hortorum Z. 5, skg. 



857. Aristea Ait. 



2683. A. pusilla Ker-Gawl. (Francke, ' Inaug.-Diss.,' Halle, 1883.) Francke 

 describes flowers of this species as homogamous, but autogamy is excluded by the 

 position of stigma and anthers. Pollination is eff'ected by means of wind or insects. 



858. Sisyrinchium L. 



Hansgirg describes all the species of this genus examined by him as bearing 

 flowers which last only for a single day (Bot. Centralbl., Cassel, xliii, 1890). 



2684. S. anceps Lam. (Loew, ' Bliitenbiol. Floristik,' p. 346; Kerner, 'Nat. 

 Hist. PI.,' Eng. Ed. i, II, pp. 190, 391.) Flowers of this North American species last 

 for only one day; Kerner states that they open between lo-n a.m., closing again 

 about 4-5 p.m. The perianth lobes are blue, with green-yellow spots at the base, 

 and are flat when expanded. They unite to form a tube about one mm. long, which, 

 according to Kerner, secretes nectar internally ; Loew states, however, that this does 

 not exude in free droplets. The filament-tube surrounding the style bears the 

 outwardly directed anthers, which dehisce while still in the bud and are at first 

 exceeded in length by the stylar branches. Autogamy is possible towards the end 

 of anthesis, the perianth then elongating so that the stigmas come into contact with 

 the pollen adhering to the inner side of the perianth. Kerner states that in 

 unfavourable weather automatic self-pollination takes place pseudo-cleistogamously, 

 as the flowers remain closed. 



Visitors. Loew (Berlin Botanic Garden) observed small bees (Halictus 

 minutissimus K. 5, skg.). 



859. Tigridia Juss. 



2685. T. Pavonia Ker-Gawl. Duchartre says that the flowers of this species 

 usually begin to open between 5-6 a.m. and are full-blown at 10 a.m. Between 

 2 and 3 p.m. they begin to fade, and are completely withered at 5 p.m. 



860. Hermodactylus Toum. 



2686. H. tuberosus Mill. (Arcangeli, Boll. Soc. bot. ital., Firenze, 1895, 

 pp. 182-4.) Arcangeli describes the flowers of this species as odourless; he says 



