A BE VIEW OF THE BRITISH CHARACEjE. 99 



as British. _ Mr. Baker, in the 'Botanical Exchange Club Beport ' 

 for 1867, gives a revision of the TohjpelltB, reducing the certainly 

 British species to two, giving C. Borreri as the var. robustior of 

 G. mtncata and mentioning C. nidijica as possibly British. In the 

 ' Joum of Bot,' 1877, Dr. Trimen adds C.fragifera to the list. 



We have followed Braun's latest opinions in dividing the order 

 into four genera, as the characters based on the position of the 

 reproductive organs, together with the difference of habit, appear 

 to warrant their separation. With regard to the varieties given it 

 must not be inferred that they are intended as subspecies, or, 

 indeed, all as of equal value, as in some instances, with the very 

 variable species, it has been thought desirable to notice as vara, 

 the more extreme forms, although they are often connected by 

 intermediates. The terms "bract-cells," "stipulodes," and 

 " spine-cells " have been employed with some reluctance, as these 

 very simple structures composed of a single cell are so like in 

 character and correlated in their variation that it seems 

 questionable whether some common term might not with 

 advantage be applied to all of them, with a slight modification to 

 denote the position. Another difficulty arises with regard to the 

 coating of the nucule which is composed of five cylindrical cells 

 from the upper portion of which the coronula is formed by a 

 transverse division. These cells, when the nucule is quite young, 

 are almost straight, but as the nucleus increases they envelope it 

 in a spiral coil. We had thought of showing the variation of this 

 covering in different species by stating the number of spirals taken 

 oy each cell when the nucule is mature, but, for the sake of 

 convenience, the practice has been followed of giving the number 

 oi lines crossing the nucule, visible from one side. 



Only those counties have been cited from which we have seen 

 ^cimens, as so many of the printed localities, of which specimens 

 oi tne plants referred to exist, have proved to be misnomers. The 

 months given are those in which the nucule is matured. 



A large number of the specimens, especially of the Nitellas, in 

 our national herbaria have been badly selected and carelessly dried, 

 and in many cases are without fruit. It indeed appears to be a 

 common idea that it is almost impossible to preserve good 

 ner barium specimens ; but no plants better repay a little care, and 

 iNordstedt and Wahlstedt's magnificent fasciculi of the Scandinavian 

 species show what may be done by thoroughly careful treatment. 

 Uur best thanks are due to Prof. Babington, who, with his 



l& 7 1 Stl ° readiness to liel P a11 in tlie stud y of our Flora, has 

 orded us much assistance by specimens and otherwise; to 



c^ u er ' Dr ' Tl 'nnen, and Mr. Britten, for their kind assistance in 

 to M r?2 g s P ecimeils and books at the British Museum and at Kew; 

 to M U ' to ^ ordste dt, of Lund, for the determination of specimens ; 

 Clio/' i ^ ore > for kindly lending us his valuable collection of 

 speci obfc aining for us the loan of the late Dr. Moore's 



Irisl! meilS '■ to * >ro ^ -Dy er > f° r an opportunity of examining his 



• in tZ 8 ,? ecimen s ; and to Mr. Curnow, of Penzance, for a very 



Cresting series of the Cornish plants. ' 



