12 



YOLANDE HESLOP-HARRISON 



The sample data of Table 1 for petal number would seem to suggest that the three 

 taxa stand in a different relationship, since the mean number of petals for N. intermedia 

 is, statistically speaking, significantly less than in the N. pumila aggregate. However, as 

 will be seen from the data of Caspary given in Table 6, in certain populations of conti- 

 nental N. intermedia the average petal number may actually exceed the average number 

 found in British N. lutea, a matter discussed further below. 



(3) Stamens. The variation in stamen shape has been observed by several authors, 

 e.g. Syme (1863) and Moss (1920). Thus, according to Syme, in N. pumila the anthers 

 are not more than one and a half times as long as broad. Koch (1843) stated that this 

 feature, among others, differentiates N. pumila from N. spenneriana Gaudin, in which 

 the anthers are said to be four times as long as broad. Planchon (1853), however, believed 



(b) ^ (c) (d) 



Fig. 4. Characteristic stamen shapes in British Nuphar taxa. 

 ■ J (a) N. lutea; (b) N. intermedia; (c) " int regressed " N. 

 (a) pumila; and (d) N. pumila. Sources of material as in Fig. 2. 



the character of anther length to be variable in N. pumila, ranging from oblong (four 

 times as long as broad) to almost square. Planchon noted that he had seen specimens 

 described as N. pumila from Scotland and America with elongated anthers. Moss (1920) 

 used anther shape as a discriminating character in dealing with N. lutea and N. pumila, 

 stating that the anthers in the former were usually four times as long as broad, and in 

 the latter about twice as long as broad. 



In the N. pumila from Lochanovie and Shropshire the anthers have a squarish form 

 (Fig. 4d) whereas those of N. lutea in all the British populations examined are considerably 

 elongated (Fig. 4a). Again N. intermedui is intermediate in this character (Fig. 4b). The 



