EXTEACTS OF PROCEEDINGS. 



cxxxiii 



LECTURE. 



Mr. Cheshire being subsequently about to lecture on bees, the 

 Rev. Gr. Henslow took the opportunity to speak principally on the 

 fertilisation of flowers by them and other insects. 



A basket of Tropaeolums furnished illustration of strong " proter- 

 andry " — i.e., the stamens, maturing first, rise up in front of the 

 orifice to the spur and then retire on sheddiDg the pollen. Subse- 

 quently the stigma matures and takes up the same position ; hence such 

 a flower is fertilised by polLen brought from a younger one. Euchsias 

 illustrated the old but false generalisation that, whether a flower 

 be pendulous or erect, the stigma will be below the anthers, so that 

 the pollen may fall upon it. Though such an arrangement is in the 

 Fuchsia the flower is proterandrous, and therefore is not adapted to 

 self-fertilisation. Moreover, when flowers are habitually self- 

 fertilised the anthers are placed in close contact with the stigmas, 

 as is the case with the 11 cleistogamous " buds of Violets. A group 

 of Pentstemons furnished the case of a flower fertilised by bees, but 

 which by means of the fifth (abortive) stamen standing over the 

 nectary, afforded an obstruction to all insects whose proboscis could 

 not reach to the bottom of the tube, and so would not be of any 

 assistance in pollinating the flower. The structure of Abutilon, 

 Malva sylvestris, and Salvia, was described as being especially 

 adapted to insects in securing cross-fertilisation, while the cleisto- 

 gamous Yiolets and Malva rotundifolia, &c, were self-fertilising. 



The lecturer observed that all the varied beauty of flowers in na- 

 ture was solely due to their being adapted to insects, whilst self- 

 fertilising flowers were as a rule inconspicuous and unattractive. 



A plant of Lygodium palmatum, exhibited byMr. Wilson, illustrated 

 the peculiarities of climbing stems or " twiners," and the lecturer 

 suggested that as the property of bowing in a circular manner was 

 not confined to climbers, for the apex of a Pine does the same, that 

 it is probably a general phenomenon of plant growth, but specially 

 utilised by plants with weak stems as a means of support. 



This suggestion has since been fully confirmed by Mr. Darwin, 

 who has shown in his work The Movements of Plants that many of 

 them are but modifications of " Circumnutatia." 



