FERTILIZATION OF SPKING FLOWERS ON THE YORKSHIRE COAST. 



187 



for insects are less likely to discriminate between the species than 

 between their sexes. MacLeod has divided the willows into eavly- 

 and late- flowering species. S. albn and frofiilis, types of those 

 flowering after the bursting of the leaf-buds, were not observed at 

 Scarborough. Using MacLeod's convenient separation, we get the 

 followin" table : — 



Yorkshire . . 

 Belgium . . 

 Germany . . , 



The want of small bees in Britain is very markedly shown. 



Comparing the individuals visiting, we notice that in the milder 

 season the long-tongued bees visited in greater numbers. Table V., 

 column E, shows this again. The bees only appeared at the very end 

 of the observations. Owing to them we get in this table (V.) two 

 maxima in the case of Saliccs, one due to the species obtaining a 

 large share of the short-tougued flies, the second due to the appear- 

 ance of these bees. The same double curve is found also in ThssUchjo, 

 where it was due to the Muscidte and Scatophagida^ relatively. It 

 is unsafe to lay any stress on the facts of these incomplete investi- 

 gations, but such cases — well established — would help to demonstrate 

 the origin of new species through seasonal dimorphism. ■' 



Narcissus Fseudo-iiarcissus. — The diameter of the cream-coloured 

 perianth is -10-50 mm., the depth of the funnel-shaped space within 

 tlje corona and tube of the flower about 45 mm., the breadth of 

 the mouth being 15 mm. The stigma and the stamens, which 

 it overtops by 4-5 mm., are well protected by the corona. Tbe 

 anthers, which burst immediately after the opening of the flower, 

 shed their pollen introrsely, in part on to the style. Large 

 insects entering the flower will touch with their backs first the 

 stigma, later the pollen-covered anthers and style, and as both 



5 and ? organs are mature at the same time, one visit is all that 

 is required. The passages to the three nectaries at the base of the 

 flower lie between the filaments, and are 1-1-5 mm. in breadth and 



6 mm. remote from the honey. Thus long-tongued insects alone 

 can obtain the honey, in fact, the flower is a most marked bee- 

 flower, and probably the scarceness of blossoms (they are very much 

 picked for the market) alone prevented me from observing the right 

 insect visitin<f the flower. 



Summary and Conclusion. 



It has been shown how the short-tongued flies predominate iu 

 early spring to a very marked extent, and that they visit freely 



in 



* Cf. Wettstein, "Der Saison-Dimorphismus als Ausgangspunkt fiir die 

 Biklung neuer Arten im Pflanzenreich," Ber. d. Dtutschen Lot. Gesellsch. xiii. 

 p. 3U3 (18UG). 



