338 Prof. Buckman on Cnicus tuberosus. 



doubted species, the grounds for which I would shortly sum up 

 as follows : — 



It occurs sparingly at Avebury, surrounded by the true Cnicus 

 acaulis and Cnicus acanthoides in great abundance. 



Its most important distinctive character will be found in the 

 radical tubers, which, in full-grown examples, are somewhat 

 large and fleshy, and unilaterally placed on the rhizome. In 

 smaller specimens the roots are long and flexile, but not ex- 

 panded into tubers, — which is just the state in which they occur 

 in the Cnicus acaulis. 



It is true that it cannot be described as acauline, as the stem 

 is more than a foot in height, but this is also often the case with 

 the true acaulis, as we have now before us examples of this spe- 

 cies several inches high. 



From these circumstances, in connexion with the rarity of the 

 tuberous form in a plant that seeds so abundantly, each head of 

 flowers being capable of perfecting as many as 150 seeds, — 

 taking also into consideration the well-known sporting propen- 

 sity of this genus, — I cannot help thinking this to be a hybrid ; 

 and from the fact of the abundance of the two forms before indi- 

 cated in its immediate vicinity, we may not unreasonably look 

 upon them as the origin of our tuberous type. 



There is perhaps no genus of plants more perplexing to the 

 botanist than that of Carduus, which is now made to include 

 Cnicus ; hence the variation in the number of species in our 

 dififerent floras; and thus Babington heads his descriptions 

 of them with the following significant note — "many hybrids 

 occur in this genus *j^^ and my friend Lees has kindly furnished 

 me with the following nOte upon another disputed species, which 

 bears directly upon this question : — 



" In August 1856, I found the Cnicus Forsteri of Smith, in 

 a field near Crowle, Worcestershire. In the same marshy field 

 was a considerable quantity of Cnicus pratensis and a very nu- 

 merous growth of C.palustris, The position of Forster^s Thistle 

 was between the C. pratensis and C, palustris, so as to give rise 

 to an immediate suspicion of its hybridity ; and, upon examina- 

 tion, the characters shown by C. Forsteri were exactly interme- 

 diate also. The leaves were much like those of C palustris, 

 while the stem and flowers were in small clusters, instead of 

 being single as in the latter. Indeed, the result of my examina- 

 tion convinced me that C. Forsteri could be only a hybrid ; and 

 this I stated in an account I sent to the 'Phytologist,^ and which 

 appeared in the September Number of that Journal for 1856.^^ 

 For the present, then, I must content myself with having 



* Manual of British Botany, 3rd edition. 



