39Q ANGIOSPERMAEDICOTYLEDONES 





When the homogamous flowers open the anthers of the outer stamens dehisc 

 while those of the inner ones remain for some time beneath the receptive stigma 

 As most of the visitors settle in the middle of the flower, and therefore tow 

 the stigmas first, they regularly effect crossing. Only the honey-bee usually push' 

 in between the petals and stamens to reach the nectar, and so may effect sel 

 pollination as well. Failing insect-visits, Stadler says that automatic self-pollinatic 

 is possible, while Focke and Waite state that the species is undoubtedly self-fertil 

 Large fruits often contain only empty pips. 



Focke describes the species as andromonoecious. When hermaphrodite flowe 

 are dusted with pollen taken from the male flowers of the same plant they a: 

 almost always sterile, though they are fertile with pollen taken from another plant. 



Visitors. Herm. Muller observed the following. 



A. Coleoptera. Coccinellidae: i. Rhizobius litura F., creeping about in tl 

 flowers. B. Diptera. Muscidae: 2. Lucilia cornicina F. C. Hymenopten 

 Apidae : 3. Andrena albicans Afull. 5, vainly searching for nectar, and then po-dvg 

 4. A. fulva Schr. 5, po-cltg. ; 5. A. gwynana K. 5, do. ; 6. Anthophora pilipes F. 

 and $, skg. ; 7. Apis mellifica L. $, generally skg., now and then also po-cltg 

 8. Bombus muscorum F. 5, skg. ; 9. B. pratorum 5 and 5, persistently skg. ; 10. 1 

 rajellus K. 5, skg.; 11. B. terrester L. $>, persistently skg. ; 12. Halictus rubicundt 

 Chr. 5, po-cltg. 



Alfken noticed the following bees at Bremen : 1. Bombus agrorum F. $ ; 2. 1 

 derhamellus K. $> ; 3. B. lucorum L. 5 and 5 ; 4- Halictus calceatus Scop. $. 



Schletterer, at Pola, saw the southern humble-bee Bombus argillaceus Scop 

 flying about the flowers on quiet sunny days in January. 



931. C. vulgaris Pers. ( = Pyrus Cydonia .). (Dodel-Port, 'Biol. Atlas < 

 Botanik'; Kirchner, ' Flora v. Stuttgart,' p. 428.) The large reddish-white flowei 

 of this species are protogynous. The nectar is protected against small unbidde 

 guests by hairs on the style, and by the incurved bases of the filaments. Sma 

 creeping insects are kept out by the recurved sepals, which are covered wit 

 glandular hairs below, and also by the thick hairs on the bases of the petal; 

 In other respects the mechanism agrees with that of Crataegus Oxyacanth; 

 Automatic self-pollination is not excluded. 



Visitors. Loew observed a bee (Halictus nitidiusculus K. 5), po-cltg., in th 

 Berlin Botanic Garden. 



266. Pyrus L. 



White or red protogynous flowers of considerable size; with half conceale 

 nectar secreted by the receptacle. 



932. P. Malus L. (Hildebrand, ' D. Geschlechts-Vert. b. d. Pfl.,' p. 60 ; Hern 

 MUller, ' Fertilisation,' p. 238 ; Kirchner, ' Beitr'age,' pp. 36-8 ; Waite, ' Pollinatio 

 of Pomaceous Fruits.') Hildebrand was the first to figure the projecting positio 

 of the stigmas owing to which cross-pollination is favoured, and Hermann Miille 

 first noticed protogyny in this species. To Kirchner we are indebted for the mo.' 

 exhaustive study of the flower mechanism. The size of the widely expanded reddish 

 white or rose-coloured blossoms varies with the variety ; in small-flowered one 

 the average diameter is 38 mm., in large-flowered ones 49 mm. During the da 



