204 ON ZVGODON HUPESTRI?. 



base, and gradually becoming slightly narrower to near the apex, 

 where it is very suddenly narrowed oil" to the excurreut nerve — 

 indeed the leaf is much more nearly ligulute than in the typical 

 form ; the nerve is deeply coloured, semi-transparent, and distinctly 

 excurrent into a short mucro, and is rather rigid throughout its whole 

 length. The whole plant also partakes more or less of a brownish-green 

 tint. In the Irish plant from Basaltic rocks in Gleno, Co. Antrim, the 

 leaf is of the same shape and tint, the nerve thick, semi-transparent, 

 in the older leaves almost opaque, and coloured, but not quite so 

 deeply as in the Swedish plant, quite as much excurrent, and, like it, 

 very prominent at the back. 



A plant gathered by the late W. Wilson at Beaumaris in Nov., 

 1867, and labelled by him Z. viridissi?mcs, var. Stirtoni, presents us 

 with the same shape in the leaf; the nerve is distinctly excurrent, 

 reddish at the base only in the younger leaves, but throughout its 

 whole length in the older and fully developed ones. 



Of a number of specimens from Scotland, from llev. J. Fergusson, 

 No. 1, from Troup, 18C9, has the nerve very strong and slightly 

 thickened at apex like the preceding ones, and in all respects agrees 

 with the other forms. 



No. 2, also from Troup, 18G9. I find from my notes tliat in the 

 full-grown leaves the characters are almost exactly similar ; in one or 

 two of the leaves the nerve seemed to vanish when looked at from the 

 upper side, but on varying the light from the reflector and altering 

 the focus a little it could still be distinctly traced to the apex, though 

 not quite so much excurrent ; still in the majority of the leaves it wa.s 

 quite as much excurrent as before. Other characters the same. 



No. .3, labelled Z. Stirtoni, Forfarshire. The nerve is not always 

 deeply coloured, but is always excurrent ; in other respects tlie same 

 as before. 



No. 4, Forfarshire. Some of the leaves are slightly more acute or 

 less obtuse than usual, but in all other particulars the same. 



No. 5, Forfarshire. Mr. Fergusson writes of this as "an in- 

 termediate form, with nerves sometimes excurrent and pellucid and 

 sometimes not," but the latter is only the case in the leaves of the 

 innovations, and even in them it is quite excurreut, and all the older 

 leaves are remarkable for their strongly projecting excurrent nerve, 

 thickened at apex, and the ruddy-green colour of the -whole plant. 



No. 6, Forfarshire, presents the same characteristics as tlie last. 



A small scrap from Mr. J. Gr. Baker, of Kew, from the " Basalt- 

 wande des lliedberg, G. A. Geheeb," labelled Z. rupestris, Schp , 

 certainly seems more like an intermediate form ; tlie plant is 

 generally much greener, the nerve thinner, transparent, not often 

 brownish, and very nearly always vanishing. Except for its high 

 authority, I should be inclined to refer it to viridissimns. 



Another plant, gathered by Mr. Briggs on walls at Plymouth, 1869, 

 labelled Zi/ffodon ?, kindly sent by Mr. Baker, is almost the exact 

 counterpart of Geheeb's plant. 



Now the question arises, should the almost ligulate, suddenly 

 tapered, and rather obtuse pointed leaf, terminating in a mucro formed 

 by a strong, ruddy, scarcely transparent, excurrent nerve, warrant the 

 separation of this form into a separate specie s. under the title Z. 



