342 THE HIGHER DICOTYLEDONS. 



flower to stigma of short-styled flower, and vice versa) yields better 

 results (more seeds germinate and stronger seedlings are produced) 

 than "illegitimate" cross-pollination, while both kinds of cross- 

 pollination are better than self -pollination. However, the manner in 

 which the pollination of the Primrose actually occurs in nature has 

 been for many years the subject of conflicting statements by various 

 observers. 



The following extracts from a paper by Professor Weiss (New 

 Phytologist, 1903), based on observations made in Shropshire during 

 the Easter vacation of 1903, are given not merely because they are of 

 interest, but in the hope that they may induce observers in various 

 parts of the country to take up the subject. 



The chief insects seen visiting the flowers were species of short- 

 tongued burrowing-bees (Andrena), hive-bees (Apis), small humble- 

 bees (Anthophora), large humble-bees (Bombus), and a fly called Bom- 

 bylius (see Art. 266). "Considering the regularity of the visits of 

 Bombylius and the relatively large number observed in really fine 

 weather, I have no doubt that this insect is an active agent in the 

 pollination of the Primrose. It seems admirably adapted to obtain 

 nectar from the depths of the tubular corolla with its long proboscis, 

 and it seemed at this time of year to confine its attention to the 

 Primrose. Only on one occasion did I observe a Bombylius sucking 

 nectar from the Celandine, which is so largely visited by the bees. . . . 



"On five different occasions I have observed Bombus visiting Prim- 

 roses, and generally in such a manner as to ensure the pollination of 

 the flowers. In two cases, however, I noticed the humble-bee not 

 sucking at the flower, but moving all over the corolla, apparently 

 endeavouring to obtain the honey by illegitimate means, just as 

 Darwin observed them at times biting through the corolla in the case 

 of the Cowslip, of which they are regular visitors. I ought to state 

 clearly that Bombus was a more frequent visitor of other flowers than 

 the Primrose, and was more commonly seen on the Willow, the 

 Dandelion, the Violet, and the Barren Strawberry. A smaller humble- 

 bee, however, Anthophora, though less plentiful in the district, was 

 more often seen on the Primrose, to which it seemed to confine its 

 attention. There can be no doubt that this insect is both able to 

 gather honey from the Primrose flower and also to effect its polli- 

 nation. 



"The honey-bee, Apis melliftca, appeared to be less hardy than the 

 humble-bee or Bombylius, for it only gathered honey on warm days 

 and was not observed at all on several days when Bombylius, Bombus, 

 and Anthophora were about. The bees visited chiefly the Celandine, 

 Barren Strawberry, Wood Anemone, Violet, and Dandelion. Occasion- 

 ally a stray one would visit a number of Primroses, but did not spend 

 much time on each. They were evidently endeavouring to obtain the 

 nectar, which however they were unable to reach. They stayed a little 

 longer on the short-styled flowers, from which the}' collected a little 

 pollen. They were obviously not the regular visitors of the flowers, 

 although they could no doubt bring about cross-fertilisation of the long- 

 styled forms. 



