254 



P. F. YEO 



Table 1. 



Characters of the Euphrasias at Withypool 



Name 

 Collector's Number 



E. anglica 

 E187B 



E187A 



E. anglica X 

 micrantha 

 E185C 



E. micrantha 

 E185A 



Intemodes 



Short 



Long 



Long 



Long 



Position and length 

 of branches 



Basal, not much 

 exceeded by main 

 stem 



Central, much ex- 

 ceeded by main 

 stem 



Central, much ex- 

 ceeded by main 

 stem 



Central, much ex- 

 ceeded by main 

 stem 



Leaf shape 



Broad 



Narrow 



Narrow 



Narrow 



Anthocyanin in 



(a) Leaves 



(b) Stems 



None 

 Little 



Upper surface in 

 some plants 

 Much 



Upper surface 

 Much 



Upper surface 

 Much 



Foliar glands 



Long, dense 



Long, dense 



Shorter, sparse 



None 



Corolla length 



6-5-8 mm. 



6 -5 -7 mm. 



Smaller than El 87 A 



5-6-5 mm. 



Corolla-lip breadth 



5*5-6*5 mm. 

 (E 180, cult.) 



4-5-5 mm. (cult.) 





3-5-4-5 mm. 



Corolla colour 



White, upper lip 

 sometimes lilac 



White, upper lip 

 sometimes lilac 



Faint lilac 



White, with ma- 

 genta upper lip, or 

 medium lilac, or 

 intense red-purple 



Capsules 



Large, broad 



Large, broad 



None 



Small, narrow 



Normal- looking 

 pollen 



98 per cent. 



98 per cent. 



3 per cent. 



95 per cent. 



Chromosomes at 

 nneiosis 



Not counted, but 



XX V diCllL-O LXx Llllo 



sp. at several other 

 other localities 



n = 11 



fPlate IS fi(T 2) 



Approximately 11 



bivalpnt^ anrl 1 1 



univalents 



About 22 bivalents 



Habitat 



Closely grazed turf 

 and paths 



Longer grass 

 around bushes of 

 Calluna, Erica cine- 

 rea,Ruhus and Ulex 



One plant only, 

 with E 185A 



Periphery of Cal- 

 luna and Erica 

 cinerea bushes. 



it for specific recognition. This is ruled out, however, on account of its distribution as 

 at present known. 



Interpretation of the Situation at Withypool 



The observations show that it is possible for triploid hybrids between diploid and 

 tetraploid species to occur. They also show strong evidence of the occurrence of plants 

 of similar parentage which are fertile and have the diploid chromosome number. Meiosis 

 in these plants is usually, at least, quite normal, as can be seen in plate 18, fig. 2, where at 

 the end of the second meiotic division there are four groups of eleven chromosomes. The 



