86 



BRITISH CHAEOPHYTA. 



The counties and vice-counties cited under the 

 several species are those from which we have actually 

 seen specimens, with a very few exceptions, and in 

 these the authorities are stated. It has not as a rule 

 been considered safe to depend on j)rinted records, so 

 many extraordinary cases of incorrect determination 

 having occurred, even by botanists of high standing. 



In the arrangement of genera and species we have 

 in the main adopted that of Braun and Nordstedt's 

 ' Fragmente,' but have followed Professor Hy in 

 separating NiteUopsis from Lychnothamnits, and, 

 among the Gharse iliflosteplianse diplostichse, have 

 placed the sub-section aulacantlise before the tyla- 

 cantJise, since among British species some of the 

 latter appear to be more nearly allied to the section 

 triplostichse than any of the former. No linear 

 arrangement can be entirely natural, and the separa- 

 tion of some closely allied species (e.g. G. vulgaris 

 and G. contraria) is inevitable. 



We have adopted the designations Anarthrodadylse 

 and Arthroclactylse for the primary divisions of Nitella 

 in preference to those employed by Braun, viz. 

 Monarthrodadylas, Diarthrodactylse, and Polyarthro- 

 dactylse, for the following reasons : — the first of 

 Braun's names does not appear to be etymologically 

 correct for the purpose to which it is applied, the 

 " dactyl," i.e. the ultimate ray, not itself possessing any 

 joint, though jointed to the limb below. The human 

 finger could hardly be described as one-jointed, if 

 it had but a single bone. Similarly Diarthrodactylse 

 is open to objection, since normally the 2-celled 

 "dactyl" has but one joint or division. We combine 

 Braun's second and third sections in view of the 

 difficulty of drawing a satisfactory line between 

 them. We have not adopted Professor Hy's sections 

 Fm'cinitella and Coniitelln, as the characters upon 

 which they are based can be applied to European 

 species only. 



The Charophyta are extremely plastic, most species 



