CREPIS XUDICAl'LTS L. AXD I.EONTODOX IIIRTUS L. 10-') 



Villars' name as synonymous with Thrincia hisjnda instead of with 

 T. hirta (Catalect. Bot. iii. p. 103), an error repeated by Gaudin, 

 n. Helv. V. 49 (1829), under the name, there appearing for the 

 first time, of Thrincia taraxacoides. Koch, however, Syn. ed. 2, 

 p. 480 (1843), and ed. 3, p. 358 (1857), protests " T. liispida 

 Koth=T. maroccana Pers. per en'orem in Flora nostra introducta 

 fuit." Gaudin's T. taraxacoides was therefore stillborn and must 

 be itrnored *. 



THE LAMELL.E OF POLYTRICHUM. 

 By W. R. SHERRijf. 



The determination of certain species of Poli/tricJmm has proved 

 more or less difficult to bet^inners on account of the superficial I'esem- 

 blance of allied forms. This difficulty is largely due to the reluctance 

 of the student to prepare thin transverse sections of the leaf, which 

 would show the diff^erence at once. Two of the most troublesome 

 spL'cies to separate without recourse to transverse sections are P. coui- 

 mnne and P. formosum, and it occurred to me to examine a number 

 of specimens of these to determine how they might be distinguished 

 more readily and without using the razor. 



The most satisfactory results were obtained by scraping the 

 lamellie off the surface of the leaf. In this way preparations were 

 quickly obtained which afjiorded a good lateral view of the lamelUe ; 

 and on comparing similar preparations of the two species, it was 

 obvious that the plants could be easily separated by the chai'acters 

 of the cells of the upper marginal rov/. The grooved margin of 

 P. commune, though more distinct in transverse section, can still be 

 made out by careful focussing, for it tends to give the edge a confused 

 or doubled margin ; whereas in P. formosum the edge appears simple 

 and sharply defined. In the accompanying illustration (p. 106) the 

 upper figures illustrate the latei-al view of the lamelUe, the lower 

 figures show these lamelb.e in transverse section. 



The gnmjMng of these and the remaining species of Poli/lrichnm 

 by characters derived fi-om the lateral view of the lamella' is very 

 distinctive, and coincides with the systematic arrangement already 

 in use in the Ilandhooh of British Ifosses by Dixon and -lameson. 

 The groups may be tabulated thus: — 



I. P. naninn, P. aloidrs. III. P. pili/'rrion, P. junijjrri- 



11. P. iirni(/erum, P. alpiniim, 

 P. Hfxaiiyulare. 



niim, P. strict nm. 

 IV. P. qracile, P./'oniiosi/m. 

 V. P. commune. 



* T. hixpidfi is an annual species from Spain, Morocco, Madeira, &c. A mis- 

 print has crept into Mr. Britten's synonymy, op. cit. p. o8, ThrinrUt nmJicnnlis 

 Lowe, Prim. Fl. Mad. does not belong to 2'. hirta but to T. tiiapida, as stated by 

 Lowe himself in Man. Fl. Mad. p. o32. 



