Robertson — Flowers and Insects. 155 



cons5picuous parts. The three inner ones secrete nectar on 

 their roui^heued inner faces, and are shaped and disposed so as 

 to require the insects to come in contact with the anthers and 

 stiojmas. At first they are not so widely expanded, and this 

 is important, since, when the flies crawl in, they are more apt 

 to touch the stigmas, which are much fewer than the anthers 

 and occupy a more limited and central position. Flies land 

 upon the backs of the petals and crawl around to the underside, 

 so that they strike the anthers and stigmas with their backs. 



Asimina is an American genus, but there seems to be no 

 reason why plants transferred to Europe should not be ex- 

 pected to show a quite natural assemblage of visitors, at least 

 in the case of the species in question, since they would become 

 exposed to a similar insect fauna. At Firenze, Delpino cap- 

 tured on the flowers a number of flies, which were determined 

 by Rondani as follows : — 



Muscidae: {\) Calliphora erythrocephala Mgn.; (2) Lucilia sericata Mgn.; 



(3) Cyrtoneura pasquorum Mgn.; (4) C. stabulans Fll. ; (5) C. assimilis 

 Fll.; Anthomijidae ; (6) Honaalomyia prostrata Rossi; Ortalidae: (7) Platy- 

 stoma umbrarum Mgn. 



Delpino did not seem to hold that the flower was adapted 

 to flesh-flies until later (4). The following list observed on 

 May 5th confirms this view. The trees are common on creek 

 banks and bloom from April 22 to May 15. 



Syrphidae: (1) Syrphusamericanus Wc!.,one; Tachinidae: (2) Masicerasp., 

 one; Sarcophagidae: (3) Cynomyia mortuorura L,, f req. ; (4) Sarcophaga 

 aegra Wlk.; (5) Helicobia sp.; (fi) H. helicis Twns.; Muscidae: (7) Lucilia 

 caesar L. ; Anthomyidae : (8) Piiorbia fusciceps Zett. ; Cordyluridae: (9) 

 Scatophaga squalida Mgn. 



On the pollination o^ Asimina triloba see: — 



(1) Delpino, Ulteriori osservazioai. Ft. I: 281, 242. Ft. 11. fasc. 2: 24, 53, 

 94, 17G, 178,214, 301, 314. Atti d. soc. Ital. d. Sci. Milano 12: 221, 232. 

 1869. 10:172-3,201,242,324,326. 1873. 17:—. 1874.— f2) Hildebrand, 

 F. Delpino's Weitere Beobaclitimgen iiber die Dichogamie im Pflanzenreich. 

 Bot. Zeit. 28: 672. 1870.— (3) Miiller, Fertilization of Flowers, 90. 1883.— 



(4) Delpino, Sulla impollinazione dell' Arum Dracunculus. Malpigbia 3: 

 389(5). 1890. (Just 181: 470). 



Podophyllum L. — Loew (1) regards the two species of 

 this genus as pollen-flowers. They are devoid of pathfinders. 



