PART III. | THE MECHANISMS OF FLOWERS. 567 
Fig. 186). <A fly, starting from a petal, usually applies its 
tongue to the honey-drops one by one, and after each it strokes 
an anther with its labelle; in so doing it may bring various 
parts of its body in contact with the anthers; but, as a rule, 
the parts which come in contact with the anthers are not those 
which come in contact with the stigmas in the same flower. | 
I have not determined whether self-fertilisation takes place in 
absence of insects. 
Visitors: Diptera—Syrphide: (1) Eristalis sepuleralis, L. ; (2) Syritta 
pipiens, L., both ab. ; (3) Ascia podagrica, F., very freq. ; (4) Melanostoma 
mellina, L. ; (5) Melithreptus scriptus, L.; all sometimes sucking, sometimes 
eating pollen. 
Alisma natans, L.—In floods, the flowers remain closed below 
the surface of the water, and fertilise themselves (351). 
Orv. VAIADACE 2. 
The plants of this order are anemophilous or hydrophilous. 
The proterogynous flowers of Zriglochin palustre, L., have been 
figured by Axell (17). 
The species of Potamogeton are distinctly anemophilous. The 
proterogynous flowers of P. perfoliatus, L., have been figured by 
Axell (17, p. 38). 
Posidonia is supposed by Delpino to be a grass adapted for a 
submerged life (178). 
Zostera is considered by Delpino to be an Aroid modified for a 
submarine existence (178, 11.). The mode of fertilisation of Zostera 
marina, L., is described by Clavaud (138) and Engler (223). 
Orv. CYPERACEAE. 
The plants of this order are throughout anemophilous, but, 
like the grasses, they are by no means without occasional insect- 
visits. I have very often seen Melanostoma mellina, L., busy on 
the anthers of Scirpus palustris; my son Hermann has seen 
several specimens of the hive-bee collecting pollen on Carex 
hirta, L., and I have watched the same insect doing so on 
Carex montana, L. 
