18 



YOLANDE HESLOP-tiARRISON 



It has unfortunately not yet been possible to observe the course of meiosis in N. 

 intermedia. That this is irregular is suggested by the low pollen fertility of the Chartners 

 Lough plants, c. 15 per cent. This contrasts with a pollen fertility of c. 97 per cent in 

 N. lutea (plants from Ellesmere), c. 85 per cent in the Avinlochan colony and c. 95 per 

 cent in N. pumila (plants from Lochanovie). The average diameter of the fraction of 

 perfect grains produced by the Chartners Lough N. intermedia was 45-57 ± 041 and 

 this is not significantly different from the pollen diameter of N. lutea (44-9 ^l it 0,30) 

 although significantly greater than that of the pollen of N. pumila (42-87 ft it 0-34). 



(a) (b) (c) 



Fig. 10. Somatic chromosomes in British Nuphar taxa. (a) N. lutea from Esthwaite Water; (b) N. intermedia 

 from Chartners Lough; and (c) N. pumila from Shropshire ( x c. 3,000). 



Infertility is equally well marked on the female side in N. intermedia. Whereas 

 ripening of the fruit proceeds quite normally, a high percentage (c. 80 per cent) of ovules 

 aborts, so that the loculi of the ripe fruit are very irregularly filled. Among the seeds 

 which do set there is considerable variability in size (range in maximum length : 2-00-5-00 

 mm., M = 4-06 dz 0-08). The range of variation is smaller in both N. lutea (range 

 3-50-5-00 mm., M = 4-96 ± 0-05) and in N. pumila (range 2-00-4-00 mm., M = 3-32 ± 

 0-05). 



Attempts to germinate N. intermedia seed were made during 1952. Fruits from 

 Chartners Lough were allowed to rot in water and the seeds collected immediately they 

 were released. Germination actually began in these N. intermedia seeds more rapidly than 

 those of N. lutea or N. pumila collected and ripened in the same season. Of a total of 

 102 seeds, 7 germinated within two months of release and initial growth was vigorous. 



N. intermedia elsewhere in the British Isles : the Evidence of Herbarium Material 



To supplement the study of N. intermedia in Chartners Lough twenty specimens 

 of British plants referred to N. intermedia preserved in various herbaria have been examined. 

 The localities from which these were collected are those indicated in Fig. 1. These 

 herbarium specimens may be taken to represent a fairly random sample from the taxonomic 

 unit " N. intermedia " as it has been interpreted by British botanists. In Table 4 the 



Table 4 



Meristic and size data for floral characters in British Nuphar taxa {ex herhariis', localities as in Table 3). 



Taxcn 



Sepal 



Carpel 



Peduncle 



length 



width 



number 



diameter 



diameter 



N. pumila 

 N. intermedia 

 N. lutea 



16-77 ± 0-28 

 19-09 ± 0-22 

 29-16 ± 0-57 



10-52 ± 0-18 

 15-11 ± 0-71 

 23-69 ± 0-70 



9-53 ± 0-29 

 10-53 ± 0-36 

 15-58 ± 0-30 



5- 62 ± 0-26 



6- 29 ± 0-19 

 10-31 ± 0-25 



3- 86 ± 0-09 



4- 67 ± 0-27 

 6-33 ± 0-21 



(All size measurements in mm.) 



