EFFIE M. ROSSER 



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population only in their greater luxuriance. Mr. Green reports that the species has 

 spread slowly in the area since it first appeared; since it seems probable that it will 

 eventually spread to other areas some notes on the distinction between S. camhrensis and 

 radiate forms of S. vulgaris, S. squalidus and S. X haxteri are given below. 



(1) Radiate forms of S. vulgaris L. / 



S. cambrensis may be distinguished in the field from all these forms by its more 

 robust habit, broader, generally more numerous ligules of the ray florets, and the longer, 

 more sparsely pubescent but longer-haired cypselae shown in Fig. 2 (d) and (e) (cypselae 

 < 2-5 mm. in S. vulgaris); older plants of the polyploid may be distinguished also by 

 the woody base of the stem. Comparison of the pollen grains (three-pored and 20-25 

 in diameter in S. vulgaris) may also be used in determination of herbarium material or 

 fresh material in the laboratory. 



(2) S. squalidus L. 



The more prominent auricles of the upper cauline leaves, the smaller, less broadly 

 campanulate involucres, short, ovate ligules, and the larger, long-haired cypselae distin- 

 guish the polyploid from all forms of S. squalidus (cypselae < 2'5mm.). As in S. vulgaris, 

 pollen grains of S. squalidus are smaller and only three-pored (20-25 /x in diameter). 



(3) S. X haxteri Druce. 



Discrimination between this hybrid and S. camhrensis in the field may be more 

 difficult; the high percentage of abortive fruits in the hybrid is likely to prove the best 

 guide. At the end of the season, however, when, as Mr. Green has also observed, the 

 capitula of S. camhrensis become successively smaller, the polyploid itself, like other 

 Senecio species (e.g. S. sylvaticus and S. viscosus), may produce a high proportion of 

 abortive fruits and confusion between the hybrid and the polyploid is probable. Where 

 fruits are available, those of the hybrid (judging by the small quantity of undoubted 

 hybrid seed which has been available for examination) can be distinguished by their 

 smaller size (< 2-5 mm.) and by the very short, scattered hairs with which the grooves 

 are lined. Though the pollen may contain some four-pored grains the majority of those 

 examined were three-pored (ca. 25 in diameter), compared with a high proportion of 

 four-pored grains in S. camhrensis. 



Discussion of leaf characters in general seems unHkely to prove of any value, in 

 view of the variability in leaf dissection exhibited by S. squalidus and S. vulgaris, though 

 the deeply dissected, highly tomentose developing leaves of S. camhrensis may be used 

 to discriminate between its seedlings and those of the parent species. 



Since S. vernalis Waldst. & Kit., a European annual having the chromosome number 

 n = 10 (Afzelius, 1929),' has been reported from Britain on a number of occasions 

 (though probably always erroneously) it may perhaps be usefully stated here that akhough 

 young plants of S. vernalis bear a superficial resemblance to those of the polyploid S. 

 cambrensis they may easily be distinguished from the latter by their relatively longer 

 ligules, smaller cypselae and normal small-grained pollen. Fruit characters and polieu 

 grain size and morphology also serve to distinguish the polyploid from such closely 

 related European species as S. leucanthemifolius Poir. (n — 10, Afzelius, 1949), and 

 S. rupestris Waldst. & Kit. (n = 10, Afzelius, 1924 as S. nebrodensis L.). S. abrotanij olius 

 L. var. tyrolensis A. Kerner (2n = 60, Tischler, 1950), recorded only from the Tyrol, and 

 other 12-ploid species, are sufficiently distinct from S. cambrensis to require no detailed 

 consideration here. 



