16 



YOLANDE HESLOP-HARRISON 



form; but in some individuals there is a tendency for the rays to coalesce, as in some 

 forms of N. lutea. 



(5) Peduncles. The flower stalk in N. lutea is usually 50-70 per cent thicker than 

 in N. pumila, and this difference in thickness is correlated with a difference in number of 

 vascular bundles. In N. lutea these are usually distributed in an outer ring and an inner 

 ring with a solitary central bundle (Fig. 8a). In N. pumila the central bundle and the 

 outer ring are present, but the inner ring is missing (Fig. 8d). In the peduncles of N. 

 intermedia the distribution of the bundles is much more variable, a common arrangement 

 being an outer ring and a central group of four (Fig. 8b), so, in this character again, the 

 condition is intermediate. In the Avinlochan colony the central bundle is retained, but 

 there are a greater number of vascular bundles in the outer ring, compared with N. pumila 

 (Fig. 8c). 



Vegetative Characters 



Sample data for leaf size are tabulated in Table 3, the dimensions given being maximum 

 length and width of leaf. Again N. intermedia lies between N. lutea and N. pumila, 

 approaching more closely the latter. This relationship is present also in thickness of 

 petiole and, as with the peduncle, this is reflected in the ratio of the number of vascular 

 bundles present in the petioles, the ranges in the plants examined being from 17-23 in 

 N. lutea (M = 19-81 ± 041), 8-13 in N. intermedia, 7-12 in the Avinlochan colony and 

 6-10 in N. pumila. The number of vascular bundles is constant from petiole base to 

 petiole apex. There is also some difference in the shape of the petiole in cross-section, a 

 feature mentioned in most descriptions of the species. That of N. pumila is elliptical 

 or lens-shaped (Fig. 9d) and that of N. lutea is trigonous (Fig. 9a); again N. intermedia 

 lies in between the two in this feature (Fig. 9b). The number of lateral veins in the 

 leaf ranges from 23-28 (M = 25-33 ± 0-35) in N. lutea and 11-18 in N. pumila (for the 

 aggregate sample, Pi + P2, M = 14-50 ± 0-39). In the N. intermedia samples studied 

 the range was 15-22 (M = 18-08 ± 0-53). 



Table 3 



Leaf characters of European Nuphar taxa (all size measurements in cm.). 



Taxon 



No. of lateral veins 



Leaf 



Length 



Width 



N. pumila 









P. a 



14-50 ± 0-39 



12-60 ± 0-44 



9-60 ± 0-36 



P. h 



13-86 ± 0-65 



9-87 ± 0-22 



7-38 ± 0-16 



P. c 



12-00 ± 0-36 



9-89 ± 0-15 



7-24 ± 0-15 



N. intermedia 









I. a 



18-08 ± 0-53 



14-80 ± 0-72 



10-90 ± 0-50 



I. h 



16-91 ± 0-73 



11-63 ± 0-56 



9-28 ± 0-34 



I. c 



14-33 ± 0-69 



11-10 ± 0-21 



10-09 ± 0-44 



N. lutea 









L. a 



25-33 ± 0-35 



29-50 ± 0-93 



26-16 ± 1-02 



L. h 



22-86 ± 0-64 



23-70 ± 1-46 



IS -60 ± 1-23 



Sources of material : a - living British (for localities see text); b - herbarium British (vice-county sources for 

 N. pumila : 40, 86-88, 92, 96-98, 109; for N. intermedia 68, 72, 77, 83, 85, 88, 89, 97, 109; and for N. lutea 

 6-9, 11-23, 25-39, 33, 37, 40, 41, 43, 48, 59, 70-72, 81, 86, 89, 98); c - herbarium continental European 

 (sources of N. pumila and N. intermedia include Scandinavia, the Alps and neighbouring mountain systems; 

 N. lutea from Scandinavia, central and western Europe, N.W. Russia and the Balkans). 



