1894- THE NATURAL HISTORY OF THE FLOWER. 351 



In conclusion may be mentioned some lines on which it seems 

 that profitable work may be done. Experimental investigation into 

 the origin of such phenomena as the various forms of flowers in the 

 same species is much to be desired ; also full and thorough study 

 of the flowers and insects of definite districts, especially in the tropics. 

 Our own country remains still to be investigated in this respect. 

 Isolated observations are of little value ; the mechanisms of almost 

 all the species of the British flora have been described — on conti- 

 nental plants. We need a thorough study of the whole flora of 

 certain regions, having regard to the composition of the flora, the 

 time of year, the insect visits, the vegetative reproduction of the 

 plants, the exact sizes of their parts, and a comparison of the 

 mechanism with that of the same plant as elsewhere observed. As a 

 model of such work may be taken Macleod's last paper on the 

 flowers of West Flanders. As another line of research, may be 

 suggested the comparison of the same flower as regards size of 

 parts, mechanism, visitors, etc., at different times of year, having 

 careful regard to the weather, in order to obtain an insight into 

 climatal effects upon the parts of the flower, the dichogamy, etc. 

 Those who have access to a botanic garden may also do useful work 

 in observing the mechanisms of exotic flowers, especially those 

 belonging to the many natural orders hitherto untouched, though, 

 owing to the absence of the proper insects, such observations will 

 necessarily be one-sided. In this connection, finally, we may 

 venture to recommend Knuth's short essay, " Ueber bliitenbiologische 

 Beobachtungen " (Kiel, 1893 : Lipsius and Tischer, i mk.), in which 

 is contained a good account of the present state of the flower-theory 

 and the methods of observation in use for this investigation. 



OUTLINE BIBLIOGRAPHY. 



Arcangeli (Cucurbitaceae), Atii congresso botan., 1892, Genova. 



Baroni [Rohdca), loc. at., and Nuovo Giorn. Bot. Ital., 1893, p. 156. 



Briquet (Galeopsis), Mem. conronnes, Acad. roy. Belg., 1893. 



Burck {Freycinetia), 's Lands plantentuin te Buitenzorg, Batavia, 1892, p. 67. 



Burkill {Medicago), Proc. Camb. Phil. Soc, 1894. 



Cobelli (Flowers and insects), Nuov. Giorn. Bot. Ital., 1893, p. 6. 



De Bonis {Platanthera), Rivista ital. sci. nat. Siena., 1893. 



Dutailly (Ceratophylliim), Bull. mem. Soc. Linn. Paris, 1892, p. 1056. 



Engler & Prantl's " Naturlichen PJlanxenfaviilien," contains many papers on floral 



biology in the numbers for the past year. 

 Focke (self-sterility), Abli. naturw. Ver. Bremen, 1893. 



Gander (flowers and insects, self-fertilisation), Natur. und Ojfenbavung, 1893-4. 

 Gibelli (Trapa), Atti reale Acad. Lincei, 1893, p. 227. 

 Giltay (Brassica, experiments on crossing and hybridisation), Bot. Jaarboek, Gent, 



1893, p. 136. 

 Goebel (water-plants), Pflanzenhiol. ScJiilderujtgen, Marburg, 1893. 

 Graebner (cleistogamy), Verli. Bot. Ver. Brandenbttrg, 1893, vol. xxxv., p. 148. 



