LABIA TAE 



291 



ably in front. The secretion is sheltered in the lowest part of the corolla-tube. Each 

 anther-lobe dehisces by a single valve. Kerner describes the lobes as resembling 

 boxes provided with covers, which spring open when touched so that pollen falls out. 

 This, however, can only be effected by bees of a size corresponding to the dimensions 

 of the flowers, and it is only these that get their backs dusted with pollen. Gynomonoe- 

 cism occasional, gynodioecism rare. 



2322. G. sp. 



Visitors. Schneider (corn-fields in Arctic Norway) observed 2 humble-bees 

 Bombus agrorum I^., and B. scrimshiranus II. (Mus. Aarsh. Troms^, xvii, 1895). 



2323. G. Tetrahit L. (Herm. Miiller, 'Fertilisation,' pp. 491-2, 'Alpen- 

 blumen,' p. 312, ' Weit. Beob.,'III, p. 48; Schulz, 'Beitrage,' II, p. 197; Kirchner, 

 'Flora v. Stuttgart,' p. 624 ; Kerner, 'Nat. Hist. PI.,' Eng. Ed. i, II, p. 356; Loew, 

 ' Bliitenbiol. Floristik,' p. 395 ; Knuth, ' Bloemenbiol. Bijdragen ' ; Mowes, Bot. 

 Jahrb., Leipzig, iv, 1883.) In this species the bright-purple corolla possesses a 

 nectar-guide on the lower lip in the form of a yellow spot traversed by a network of 



Fig. 336. GaUopsis Tetrahit, Z,., and G.ochroleuca, Lam.(a.ittT Herm. Muller). (1-3) G. Tetrahit. 

 (i) Flowers seen from the front. {2) Reproductive organs of do., seen from the front, and further 

 enlarged ( X 7). (3) Ovary {ov) and nectary () of do. ( x 7). (4-6) G. ochroUuca. (4) Relative 



position of the reproductive organs at the beginning of anthesis. (5) Do. at the end of anthesis. (6) 



Ovary {ov) and nectary (w). 



red lines. The corolla-tube, directed obliquely upward, varies between ii and 

 1 7 mm. in length. Its uppermost 4-6 mm. are so enlarged that a small humble-bee 

 can insert the whole, and a middle-sized or large one the fore-part of its head. The 

 larger humble-bees, therefore, must have a proboscis 14-15 mm. long in order to 

 suck all the nectar ; smaller ones can do so with a proboscis of 12 mm. The anthers 

 dehisce shortly before the beginning of anthesis, turning their pollen-covered surfaces 

 downwards. The two stigmatic branches are at first situated slightly above and 

 behind the anthers, so that a humble-bee visitor touches the latter sooner than the tip 

 of the lower stigmatic branches ; this is usually, however, with a different part of its 

 head, hence cross-pollination is generally effected. Later on the tip of the style 

 bends slightly downwards, so that the lower branch projects between the anthers, and 

 if the pollen has not been removed by insects, some of it falls on the stigma, effect- 

 ing automatic self-pollination. Short-tongued humble-bees obtain the nectar by 

 perforation. 



u 2 



