248 



ANGIOSPERMAEDICOTYLEDONES 



situated beneath the ovary secretes abundant nectar, which is concealed in the base 

 of the corolla-tube ; in hermaphrodite flowers this is about 3 mm., and in female ones 

 about 2 mm. long. The mouth of the flower is fully i^ mm, and one mm. in 

 diameter respectively. The nectar is therefore accessible even to short-tongued 

 insects. It is protected from rain by hairs reaching from the inner surface of the 

 corolla-tube to its middle. Hermann Muller states from actual observation that the 

 large, and therefore more conspicuous, hermaphrodite stocks are first visited by 

 insects, and the smaller, less conspicuous female ones afterwards. Gynomonoecious 

 stocks may be rare, or sporadically may be the only ones present. Hermaphrodite 

 and female ones are about equally numerous. 



Mowes also found the species to be gynodioecious, with large-flowered 

 hermaphrodite and small-flowered female stocks. 



Fig. 326. Mentha, L. (after Herm. Muller). (1-4) Mentha arvensis, L. (i) Female flower. 



(2) Hermaphrodite do., in the first (male) stage. (3) Do., in the second (female) stage. (4) Ovary {pv) 

 and nectary (). (5) Mentha aquatica, L. Female flower seen obliquely from the front, to show the 



vestigial stamens, foreshortened. a', vestigial stamens. (i) and (5) should be supposed twisted round 

 to the right into a horizontal position. 



Schulz says that the species is gynomonoecious and gynodioecious, and that 

 occasionally 50 % or more of the stocks are female. In other stations purely 

 gynomonoecious plants are to be found. He adds that the female flowers are visited 

 by insects quite as frequently as the hermaphrodite ones. Warnstorf observed both 

 gynomoecism and gynodioecism at Ruppin. 



Visitors. Knuth observed the following. 



A. Diptera. {a) Muscidae: 1. Lucilia caesar Z., skg. (^) Syrphidae: 2. 

 Syritta pipiens Z., skg. and po-dvg. ; 3. Syrphus balteatus Deg. S, do. ; 4. S. ribesii 

 Z., do. B. Hymenoptera. Apidae : 5. Apis mellifica Z. 5, very common, skg. ; 



6. Bombus terrester Z. 5, skg. 



Herm. Miiller gives the following list of insects, all skg. 



A. Diptera. (a) Muscidae-. i. Lucilia albiceps Mg., not infreq. ; 2. 

 L. cornicina F., do. ; 3. L. sylvarum Mg., do. ; 4. Onesia floralis R.-D., freq. ; 

 5. O. sepulcralis Mg., do. ; 6. Pyrellia cadaverina Z., not infreq. {b) Stratiomyidae: 



7. Odontomyia viridula F. (f) Syrphidae : 8. EristaUs sepulcralis Z., very common ; 

 9. Melithreptus scriptus Z., not infreq., skg. ; 10. M. taeniatus Mg., do. ; 11. Syritta 

 pipiens Z., freq. B. Lepidoptera. Rhopalocera : 12. Epinephele janira Z. 



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



Verhoeff" (Norderney), the Muscid Lucilia latifrons Schin. MacLeod (Flanders), 

 a hover-fly (Bot. Jaarb. Dodonaea, Ghent, v, 1893, p. 364). Scott-Elliot (Dum- 

 friesshire), several Muscids and beetles ('Flora of Dumfriesshire,' p. 135). 



