NUPHAR INTERMEDIA IN BRITAIN 17 



Scale for b)c) ond d) 



3 mm. 



(a) 



Fig. 9. Characteristic forms of petiole anatomy in British Nuphar taxa. (a) N. lutea; (b) N. intermedia; 

 (c) " introgressed " N. pumila ; and (d) N. pumila. Sources of material as in Fig. 2. 



Chromosome Number and Fertility of the Chartners Lough Plants 



The somatic chromosome number of N. intermedia was determined from root-tip 

 material of plants from Chartners Lough collected in July and fixed in Nawashin's modifi- 

 cation of Langlet's fluid. In all of the plants examined 2n = 34. This is the first count 

 reported for N. intermedia. The number 2n = 34 is the same as that determined for 

 both N. lutea and N. pumila from continental material (Langlet and Soderberg, 1927) and 

 is the same as that observed in British plants of N. lutea from Ellesmere, Esthwaite Water 

 and Monkhill Lough, and of N. pumila from Shropshire, examined cytologically during 

 the present studies. A mitotic metaphase plate from N. intermedia is illustrated in Fig. 

 10b, together with ones from N. lutea (Fig. 10a) and N. pumila (Fig. 10c), all from British 

 sources. There appear to be no characteristics of chromosome size or morphology which 

 would serve in any way to discriminate the three, 



