NOTBS ON ASTER TRIPOLIUM. 



T. FETCH, B.Sc, B.A. 



The existence of two forms of the Sea Aster is well known to 

 the naturalist who has the fortune to live near any of our 

 estuaries, and, taking- a broad view, he comes to associate them 

 with a difference in habitat without inquiring- too deeply into the 

 foundations of his belief. 



Our Floras deal with these two forms in the usual way. 

 Bentham, as revised by Hooker (Ed. 6), says : ' Florets of the 

 ray purplish, numerous or few, and occasionally wanting'; 

 Syme's ' English Botany ' (Ed. 3) makes two varieties, ' var. 

 a. gemdna. Florets of the ray ligulate, spreading, white or 

 lilac. Var. discoidens. Anthodes discoid without a ray." 

 There is, of course, no attempt to correlate form with habitat. 



In the 'Essex Naturalist' (Vol. 12, 1902, p. 237), Mr. 

 Percy Clarke notes that the Sea xyster on the salt marshes 

 overflowed at spring tides have small golden heads, but inland 

 on the side of dried up ditches or on low banks they possess 

 a ray : that in many cases the former have a few poorly- 

 developed ray florets, but the majority have none. He sugg'ests 

 that it is a case of degeneration from the rayed to the non-rayed 

 form, with a change from insect pollination to wind pollination, 

 and is supported by the Editor, who states : ' Diptera and 

 Hymenoptera frequent both forms, but in my experience are in 

 far greater profusion on the rayed.' The only other reference 

 I have been able to find is a note by Dr. Julius MacLeod (Bot. 

 Centralb., Bd. 29, p. 215); he notes that both forms grow 

 together. 



Mr. Clarke's observation as to the occurrence of the two 

 forms coincided with the impressions derived from a long 

 acquaintance with the estuaries of the East Coast, though his 

 conclusions seemed open to criticism, and to test these, an 

 investigation was instituted on the Humber shore. The 

 immediate result was surprising, for it showed that the broad 

 view hitherto held was quite erroneous, and that Dr. MacLeod 

 was correct in stating that on the salt marsh the two forms 

 grow together. 



The distribution of these forms in the Humber district is as 

 follows : — 



(i) The plants along the ditches inland possess con- 

 spicuous, rayed flower heads. 



Naturalist, 



