no INTRODUCTION 



nectar). Miiller, however, expressly remarks, that a sharp limit cannot be drawn 

 between AD and A, and that, e.g. Rhamnus, Sibbaldia and Alchemilla might 

 perhaps be indicated by AD as correctly as by A. [Employing the symbols adopted 

 in this translation E=A, F=D, and AD=EF. Tr.] 



Dull yellow flowers with exposed nectar, e. g. Anethum graveolens, Bupleurum 

 falcatum, Pastinaca sativa, were never seen (in Westphalia) by Hermann Miiller 

 ('Fertilisation,' p. 287) to be visited by beetles, but only by flies and bees, though 

 Loew ('Beitrage') observed (in Silesia) six beetles among forty-six visitors of Anethum 

 graveolens (13 %). 



Listera ovata is chiefly visited and pollinated by ichneumons, and also by 

 a beetle (Grammoptera laevis) (see ' Immenblumen,' p. 146). 



Parnassia palustris is a deceptive or pseudo-entomophilous flower (see Class 

 Fd, pp. 67-8). 



3. Flowers with partly concealed Nectar (EC.) 



This group is connected with the previous one by many transitional forms. 

 Ttie nectar is directly visible only under favourable circumstances (in bright sunshine), 

 otherwise it is more or less hidden in the recesses of the flower. The members 

 of this group are mostly actinomorphous, and not always fully expanded. They are 

 completely open only in bright sunshine, while at other times they close up into 

 hemispherical cups. They include almost all the Cruciferae and Alsineae, the 

 species of Ranunculus and Batrachium, Caltha, Crataegus, Berberis, Fragaria, 

 Potentilla, Comarum, Sanguisorba, and so forth. 



In this class of flowers, white and yellow also predominate, but these colours 

 are more intense than in the last class. White with red spots is rare (Saxi- 

 fraga rotundifolia), so are red (Ranunculus glacialis) and dark purple (Sangui- 

 sorba officinalis, Comarum palustre, Potentilla atrosanguinea). The visitors belong 

 to quite different groups of insects from those of flowers included in Class E. 

 It is true that short-tongued flies and wasps, and also beetles, still constitute 

 a considerable proportion of the floral guests, but these insects find it rather difficult 

 to get at the partly concealed nectar, so that they prefer to visit flowers with exposed 

 nectar. On the other hand, insects with a proboscis of medium length are extremely 

 common pollinating-agents in flowers of this class. The simple flowers, rich in 

 pollen, and open in the sunshine, constitute an extremely suitable field of activity for 

 small short-tongued bees possessing collecting-brisdes, as well as for hover-flies, 

 which readily eat pollen as well as honey. These are accordingly the insects that 

 above all others frequent flowers with partly concealed nectar, and it is interesting to 

 see how flowers of this kind which have migrated from Europe into North America 

 receive there a circle of guests completely comparable to the European one. 

 According to the observations of Charles Robertson, Stellaria media, for example, 

 is specially visited in Illinois by short-tongued bees and hover-flies, exactly as in 

 central Germai^y. 



As in the previous class, the circle of visitors of flowers with partly concealed 

 nectar depends upon the character of the insect fauna for the particular region under 

 observation. In districts where short-tongued bees are scarce, e. g. on the North 

 Frisian Islands, these insects are less conspicuous than the Syrphidae : in the Alps, 



