349 



the author observes that " in an extensive series of specimens, these 

 forms are united by intermediate links." In his preliminary remarks 

 he also states : — 



" When I first approached this suhject with a view to ascertain the value of the 

 characters by which the British Oaks are supposed to be distinguished, I was under a 

 strong impression, that at least, the two forms recognised as species under the names 

 of Robur and sessilrflora were really distinct. But I soon found that the ascribed cha- 

 racters were of little importance in rigid specific discrimination, and that the only one 

 of any value at all, viz., the sessile or pedunculated fruit, must be received with so 

 much latitude as greatly to weaken, if not to render it entirely unworthy of confi- 

 dence." — p. 65. 



The following remarks are made on " the characters supposed to 

 reside in the leaves." 



1. The petiole in Quercus Robur is said to be short; that is, in the 

 form so called the petiole is supposed to be shorter than in either Q. 

 sessiliflora or intermedia. In two of the figures " which certainly do 

 not represent Q. Kobur, they are shorter than in several of the forms 

 which undoubtedly belong to that plant." 



2. The general outline of the leaf. This cannot be defined " so as 

 to distinguish any of the forms as species, as they run insensibly into 

 each other. Nay, some of the forms in Q. Robur are absolutely re- 

 peated in Q. sessiliflora." 



3. The characters supplied by the strict outline of the leaf and of 

 its several parts, appear to be equally unsatisfactory. " The base va- 

 ries equally in all the forms." " In Q. Robur, although generally more 

 or less bi-auriculate, it is sometimes rounded, and even attenuated," 

 and such is the case in Q. sessiliflora also. No greater importance is 

 to be attached to the pinnatifid character of the leaf; the lobes of the 

 leaf too " are sometimes rounded, when the sinuses are acute, and vi- 

 ce versa ; and sometimes both lobes and sinuses are obtuse, at others 

 both are acute." The staiTy pubescence attributed by Prof. Don to 

 Q. intermedia, the author finds to be present in the young state of 

 almost all the forms he has figured, and it may be traced in nearly the 

 whole series of his fully developed specimens. 



" If the leaf be taken in conjunction with the peduncle, no character whatever is 

 afforded ; and I agree with Mr. Leighton, who has truly remarked that the leaves of 

 our oaks 'vary without the least reference to the absence or presence, or relative length 

 of the peduncle.' If the peduncle alone be taken as a guide, we shall in vain search 

 for an immutable character, for every intermediate state is to be observed between the 

 elongated peduncle as I have it from Cumberland, 5 inches long, and from Killin, 

 above 4 inches long, to its total absence. 



