372 ANGIOSPERMAEDICOTYLEDONES 



Bees were also observed as follows by the authorities and in the places stated. 

 Alfken (Bremen) i. Andrena albicans Mtill. $, occasional, skg. and po-cltg.; 

 2. A. albicrus K.% freq., skg. and po-cltg.; 3. Nomada bifida Ths. 5, do. Schmiede- 

 knecht (Thuringia) 1. Andrena cyanescens Nyl. ; 2. A. parvula K. Schenck 

 (Nassau) Andrena cingulata F. Friese (Hungary), Andrena genevensis, Schmiedekn.; 

 (Innsbruck) Osmia bicolor Schr. 5, only po-cltg. von Dalla Torre (Tyrol) 



1. Andrena parvula K. >; 2. Halictus nanulus Schenck &"; 3. Osmia aurulenta Pz. 

 j and 5 ; 4. Prosopis borealis Nyl. 5. Schletterer (Tyrol) 1. Halictus albipes/*. ; 



2. Prosopis communis Nyl. 



877. P. cinerea Chaix (=P. arenaria Borck.), and 



878. P. opaca L. Schulz ('Beitrage,' II, pp. 67-8) states that these two 

 species agree with P. verna as regards flower mechanism, and are visited by numerous 

 insects, especially flies, beetles, and the smaller or more rarely the larger bees. Most 

 of the visitors collect or devour pollen. 



Visitors. Loew (Brandenburg) gives the following list for P. cinerea (' Beitrage,' 



P- 38).- 



A. Diptera. Syrphidae: 1. Cheilosia praecox Zeit., po-dvg. B. Hymeno- 

 ptera. Apidae : 2. Halictus morio F. 5, po-cltg. ; 3. H. tumulorum L. $, do. ; 4. 

 Osmia bicolor Schr. t>, skg. 



Schletterer observed the following bees at Pola. 



1. Andrena parvula K. ; 2. Halictus calceatus Scop. ; 3. H. interruptus Pz.; 

 4. H. levigatus K. 5; 5. H. malachurus K. ; 6. H. morio/'.; 7. H. quadrinotatus 

 K. ; 8. Osmia versicolor Ltr. 



879. P. caulescens L. The flowers of this species are homogamous, or 

 (according to Kerner) slightly protogynous. Visitors may effect either cross- or self- 

 pollination, and the latter can also take place automatically (Schulz). 



Visitors. Herm. Mailer observed Apis, a Bombus, and a Melithreptus (' Alpen- 

 blumen,' p. 222). 



880. P. atrosanguinea Lodd. Delpino ('Ult. Oss./ p. 233) describes the 

 flowers of this species as protogynous, with stigmas that are only receptive for a 

 short time. At first the stamens are curved away from the middle of the flower 

 and their anthers are unripe, while the mature stigmas occupy the centre. The 

 stamens subsequently raise themselves to the level of the stigmas. 



Visitors. Delpino observed small bees (sp. of Andrena and Halictus) 



881. P. fruticosa L. (Herm. Miiller, ' Fertilisation,' p. 233 ; Knuth, ' Bloemen 

 biol. Bijdragen.') In this species, according to Hermann Miiller, nectar is so scantily 

 secreted that it does not accumulate into little drops; but the smooth glistening 

 ring of the receptacle surrounding the roots of the filaments is so frequently licked 

 by insects, even by the honey-bee, that it is doubtless covered by a thin layer of it. 



The flowers are homogamous. When insects alight they sometimes first touch 

 the stigmas, sometimes the laterally dehiscing anthers. The chances of cross- and 

 self-pollination are therefore about equal. Failing insect-visits, automatic self- 

 pollination sometimes takes place, the withering stamens partly bending inwards, 

 and thus bringing their anthers (to which pollen still clings) into contact with 

 the stigmas. The number of insect visitors, however, is so large that this kind 

 of pollination is scarcely likely to occur. 





