124 



P. S. GREEN 



cslls to ordinary epidermal cells (for details of the method of calculation etc., see Salisbury, 

 1927 ; or Rowson in Howard & Manton, 1946), and, despite experimentation with 

 various techniques, attempts to use herbarium material have proved unsatisfactory. 

 Thus the only diagnostic characters so far known depend upon the plant being at least 

 at the flowering stage. 



Possible Hybrids 



As has been mentioned, both subspecies have the same chromosome number and 

 Peterson (1936, 324) has reported, as the result of hybridisation experiments, that they are 

 fully interfertile, the hybrid producing well developed pollen and ovules and viable 

 seeds. These seeds are intermediate between those of the parents. According to Dr. 

 Andreas, the two subspecies are separated ecologically (at least in Holland) but there 

 seems no doubt that they do cross when they happen to meet in the wild. Lawalree 

 (1954b) has reported intermediate specimens from Belgium and there are three herbarium 

 sheets in the National Museum of Wales, Cardiff, and one in Birmingham University 

 which seem intermediate in character. These four specimens are listed towards the end of 

 this paper in the section dealing with the detailed British distribution and there seems no 

 reason to doubt that as both subspecies have been collected and recorded from the area 

 of the Wye Valley a number of intermediate plants may occur in that district. Only one 

 of the four specimens cited bears seeds, and even these are immature, but the intermediate 

 status of the plants is shown by a combination of the two characters : length of the petiole 

 of the uppermost vegetative leaf and the proportional length of the second inflorescence 

 bract to the first : see Table. 



Table 



Locality 



Length of petiole of upper- 

 most vegetative leaf 



Length 

 bract as 



of second inflorescence 

 a percentage of that 

 of the first. 



1. 



Between Bigsweir and St. 

 Briavels 



1-5-2-0 cm. 





16-56% 



2. 



Llandogo Glen 



l'5-3-5 cm. 





41-78% 



3. 



Whitebrook 



2-3 cm. 





42-71% 



4. 



Cwm Rhaiadr 



1-1-5 cm. 





32-50% 



Very few abortive pollen grains were found in three of the specimens cited above 

 and, as has been mentioned, Peterson pointed out that the pollen in the hybrid is fully 

 developed. However, whatever its significance may be, in the specimen from Cwm 

 Rhaiadr, Llyffnant Valley, the proportion of abortive grains is quite high. 



Stellaria MONTANA Picrrat. 



Amongst the Continental material in the Herbarium at Kew, I have had my attention 

 drawn by Mr. R. D. Meikle to three specimens collected in July 1879 at Gerbamont, 

 Rochesson, Vosges, France (Plate lie). This material was described as a new species : 

 Stellaria montana D. Pierrat (1880, Comptes Rendus Soc. Bot. Rochelaise, 2, 58)*. I have 



• Not the plant from Alamos, Mexico, named S. montana J. N. Rose (1891, Contrib. U.S. Nat. Herb., I, 93) which is the only 

 $. montana at present listed in the Jndex Kewensis, 



