OBSERVATIONS ON THE SPECIES OF POTTIA. 3 



To return from this digression : it will be best to spenk of these Mosses 

 under the name of Pottla, as being that by which they are best known, 

 and the British species may be separately distinguished in the following 

 manner : — 



Leaves with accessory lamellte on the nerve 1. P. cavifolia. 



Leaves without accessory lamellae. 

 Calyptra scabrous. 



Leaves obtuse 2. P. Wilsoni. 



Leaves acute 3. P. Starkeana. 



Calyptra smooth. 



Leaves serrulate towards the apex. 



Nerve not excurrent 4. P. Seimii. 



Nerve excurrent 5. P. lanceolata. 



Leaves quite entire. 



Peristome always present 6. P. ccespitosa. 



Peristome almost unknown. 

 Leaves in 5 rows. 

 Leaves smooth. 



Capsule turbinate 7. P. truncata. 



Capsule oval-cylindric 8. P. Httoralis. 



Leaves rough 9. P. asperula. 



Leaves in 8 rows. 



Nerve excurrent into a long point 10. P. crinita. 



Nerve forming a short point 11. P. viridifolia. 



1. P. ccivifoUa, Ehrh., or rather as it should be P. pusilla, Hedw., is a 

 well-marked species from the presence on the inner side of the nerve of 

 the leaf of narrow lamellae ; in this it agrees with a species not yet de- 

 tected in Britain, P. subsessilis, Brid., which from having its calyptra 

 split on several sides forms the genus Phnromitrumi, Schimper, Synopsis, 

 p. 121 ; the resemblance is, however, so great that a natural arrangement 

 must keep them in one genus. The variety of P. pusilla, with an elon- 

 gated seta and capsule, enumerated in the ' Bryologia Britannica ' as var. 

 S. gracilis, has the peristome of Desmatodon, which may be dissected 

 out of the operculum, it is then the Barbida cavifolia, Schimper, Syn- 

 opsis, p. 734, and the Tortula lamellata, Lindberg, De Tortulis, etc. 

 Having gathered this form, my own opinion is that it is only a more com- 

 plete state of P. pusilla, at the same time it must be admitted that interme- 

 diate states have not yet been found. Closely allied also to P. pusilla, are 

 Desmatodon nervosus, which has the peristome variable in length and is 

 really a Tortula, and T. chloronotos, Brid. 



2. P. Wilsoui, Hook., with its obscure octofarious leaves, is a very dis- 

 tinct species ; British specimens show hardly a trace of peristome, but 

 others gathered at Hyures, by Sir W. C. Trevelyan, have a narrow mem- 

 brane wilhin the mouth of the capsule. The inflorescence is probably 

 subject to variation, for the antheridia are sometimes included in a small 

 bud as well as being free in the axils of the comal leaves. My specimen 

 of the Entothymenium mucronifolium, MuelL, is certainly P. Wilsoni, and' 

 is only a little more complete state than the French specimens ; this syno- 

 nym should, therefore, be removed to its proper place. 



3. P. Starkeana, Hedw., or Anacalypta Starkeana, including its gym- 

 nostomous form, P. miniitula, and its intermediate states, Weissia qffinis. 

 Hooker and Taylor, or var. hrachyodm, is variable in the length of its 

 capsule, which, when very long, is also as often gymnostomous as the states 

 in which it is shorter, and presents every gradation in the amount of its 

 development of peristome, from none to that attributed to Anacalypta. Mr. 



b'2 



