340 ANGIOSPERMAEDICOTYLEDONES 



This species is, like the two preceding ones, generally dioecious (with both sexes in 

 about equal numbers), much more rarely gynomonoecious, andromonoecious, or 

 hermaphrodite. 



764. Rheum L. 



Flowers entomophilous, with half-concealed nectar. 



2464. R. Rhaponticum L. (Axel), ' Om Anord. for Fanerog. Vaxt. Befrukt.,' 

 p. 57 ; Knuth, ' Beitrage,' I.) 



Visitors. Knuth saw hover-flies (Syrphus sp.), po-dvg., on garden specimens. 



2465. R. undulatum L. (?). (Herm. MuUer, ' Weit, Beob.,' II, pp. 222-3.) 

 The crowded, greenish-yellow flowers of this species are tolerably conspicuous. 

 They secrete a small quantity of nectar from the receptacle, between the roots of 

 the filaments, and are markedly protandrous. The stigmas do not mature until the 

 anthers have withered, so that self-pollination is excluded. Insect-visits at least 

 effect geitonogamy. 



Visitors. Loew (Berlin Botanic Garden) saw the po-dvg. beetle Cetonia aurata 

 L., and Herm. Miiller gives the following list for Westphalia. 



A. Coleoptera. (a) Curcultonidae : i. Spermophagus cardui iS/ra. {b) Der- 

 mestidae : 2. Anthrenus muscorum Z. B. Diptera. (a) Empidae : 3. Em pis sp. 

 skg. (3) Muscidae : 4. Anthomyia, various sps. (f) Syrphidae : 5. Ascia podagrica 

 J^., freq. ; 6. Cheilosia sp. ; 7. Eristalis nemorum Z. ; 8. Helophilus floreus Z. 

 9. Syritta pipiens Z., freq. 



2466. R. hybridum Murr. 



Visitors. Loew (Berlin Botanic Garden) saw the Elaterid beetle Lacon murinus 

 Z., dvg. the anthers. 



2467. R. tataricum L. (?). 



Visitors. Plateau observed the following po-dvg. beetles. 



1. Cantharis fusca Z. ; 2. Phyllopertha horticola Z. ; 3. Trichius abdominalis 

 M/n. ; 4. Anthrenus sp., freq. 



765. Oxyria Hill. 



Hermaphrodite or gynomonoecious wind flowers. 



2468. O. digyna Hill (= Rumex digynus Z.). (Lindman, ' Bidrag till 

 Kanned. om Skandin. FjellVaxt. Blomn. o. Befrukt., p. 36 ; Schulz, ' Beitrage,' II, 

 p. 199; Kemer, 'Nat. Hist. PI.,' Eng. Ed. i, II, p. v.) Schulz and Kemer in the 

 Tyrol, and Lindman on the Dovrefjeld, found this species to be gynomonoecious. 

 Lindman says that the hermaphrodite flowers are first protogynous and then homo- 

 gamous ; Ekstam makes a similar statement for Nova Zemlia. Andersson and 

 Hesselman describe the species as blooming in Spitzbergen from the second half 

 of June till the end of July ; the fruit beginning to ripen from the beginning of 

 August (' Bidrag till Kanned. om Spetsbergens o. Beeren Eil. Karlvaxtflora,' p. 66). 

 Ekstam states that in Spitzbergen the flowers are feebly protogynous or protogynous- 

 homogynous (' Blutenbiol. Beob. a. Spitzbergen,' pp. 29-30). 



