258 ANGIOSPERMAE—DICOTYLEDONES 



2237. S. glutinosa L. (Sprengel, ' Entd. Geh.,' p. 63 ; Hertn. Miiller, ' Fertilisa- 

 tion,' pp. 481-2, ' Alpenblumen,'pp. 317-18; Ogle, ' Pop. Sci. Rev.,' London, viii, 1869; 

 Darwin, 'Cross- and Self-Fertilization,' p. 427 ; Kerner, ' Nat. Hist. PI.,' Eng. Ed. i, 

 II, p. 262 ; Correns, op. cit. ; Knuth, ' Bloemenbiol. Bijdragen.') — The lower anther- 

 lobes of the large yellow flower of this species are quite sterile and completely 

 retracted into the corolla-tube. The latter is so long that only humble-bees with 

 a proboscis about 14 mm. long can suck all the nectar legitimately. The corolla- 

 tube (in plants from the Kiel Botanic Garden) is 18-19 n^"^- Jon&> but widens out at 

 the entrance for a depth of 4-5 mm., so that a humble-bee can insert its entire head. 



Correns says that S. glutinosa may be distinguished from S. pratensis and related 

 species by the fact that the lower half of the connective no longer performs the 

 additional function of a nectar-cover, a special organ of this kind being present, while 

 the connective-plate presents its edge and not its surface to visitors. The unions 

 between the two anthers and the two sterile connective surfaces are very variable. 

 The membranes of the joint are here also of the greatest extensibility ; in different 

 flowers the joint resists torsion to a varying degree. 



Visitors. — The following were recorded by the observers, and for the localities 

 stated. — 



Sprengel, humble-bees. Ogle was the first to notice flowers perforated by 

 humble-bees (of undetermined sp.). Herm. Miiller (canton Graubiinden) and Knuth 

 (between Interlaken and Grindelwald) noticed the humble-bee Bombus mastrucatus. 

 Gerst. as a nectar-thief; it perforated the upper side of the corolla-tube, and sucked 

 nectar through the holes thus made. Frey-Gessner made similar observations. 

 Knuth (Kiel Botanic Garden), 2 humble-bees, skg. legitimately — Bombus agrorum. 

 F. $, and B. hortorum L. 5. Gerstacker (Kreuth), 2 bees — Bombus mastrucatus 

 Gerst. 5 and 5, and Psithyrus vestalis Fourcr. Schletterer (Pola), 3 bees — i. Bombus. 

 argillaceus Scop. ; 2. B. derhamellus K. ; 3. Xylocopa violacea L. von Dalla Torre 

 (Pola), the humble-bee B. mastrucatus Gerst. 



Loew (Ber. D. bot. Ges., Berlin, vi, 1886, pp. 128-9) also observed the- 

 humble-bee Bombus hortorum L. in the Berlin Botanic Garden ; but pollination does 

 not seem to have been effected regularly, for Loew noticed that in autumn (in the 

 middle of September) a $ of this species visited in succession about 50 flowers on 

 the same stock, but did not once touch the tip of the style with its thickly-dusted 

 back. In the majority of flowers the connective-plates were separate. 



Loew states that the sticky glandular hairs of the flower undoubtedly form 

 a protection against unbidden guests, for he found flies and ants sticking to the 

 calyx in several instances. 



2238. S. Sclarea L. (Hildebrand, Jahrb. wiss. Bot., Leipzig, vi, 1886; 

 Herm. Miiller, 'Fertilisation,' p. 479; Correns, op. cit.; Schulz, 'Beitrage.') — The 

 flower mechanism of this species essentially agrees with that of S. pratensis, but 

 Correns found a firmer union between the filament and connective ; the membrane 

 of those epidermal cells of the joint nearest the filament being considerably thicker 

 than that of the cells adjoining the connective. The spoon-shaped plate formed by 

 the lower ends of the connectives does not completely close the entrance to the 

 nectar, and there is therefore a reduced nectar-cover in the corolla-tube in the form 

 of a small fringed scale. Schulz observed female stocks as well as those bearing 

 protandrous hermaphrodite flowers. 



