©tn'gtnal ^vtidt^. 



ON A NEW SPECIES OF IS0ETE8 FEOM IRELAND. 

 By D. Moore, Ph. D. 



(Tab. 199.) 



IsoETES MoREi. — Corm bilobed, somewhat crescent-sliai^ed at 

 base, the extremities of crescent pr^emorse, transverse section of 

 corm panclm-aeform in shape, nearly twice as long as broad, with a 

 slight transverse median line from furrow to fm-row wddening in 

 the centre, solid, of compact tissue ; roots smooth, dichotomously 

 branched; leaves numerous, as many as twenty from one corm 

 occasionally, very long, varying fi-om one to two feet or more, 

 slender and flexible, tapering gradually to a setaceous point, semi- 

 circular, with wide diaphanous sheaths involute at margm w^hich 

 nearly meet at base and j)artly overlap the sporangia, colour 

 bright green, lacunes large, tissue loose ; macrosporangia com- 

 paratively small, in saccate compartments at the bases of the outer 

 leaves, each containing about twenty spores, veil well developed, 

 arched and covering the s^^orangia two-thirds of their length ; 

 lingula triangularhj ovate-cordate, as broad as long, of a bromiish 

 colour in centre, with diaphanous margins, the latter comi)osed of 

 layers of single cells and more or less entire according to the equal 

 growth of the delicate cells ; Ugula short, ovoid, with glossopodium 

 and glands rather mdistinct ; macrospores roundish or slightly 

 triangular, granular on surface especially on basilar half ; micro- 

 spores smooth, or slightly crested on convex margin. 



Hc(b. — Upper Lake Bray, County Wicklow, Ireland, where it is 

 always submerged. 



Compared with its nearest ally, Isoetes laciistris, this remarkable 

 form differs in the following particulars : — First, in the leaves being 

 more numerous on strong x^lants, from three to four times longer 

 than they are in the normal state of that species, only half the 

 diameter, more setaceous, lacunes longer, and tissue looser. 

 Second, in the much broader sheaths of the leaves, which are 

 more involute at their margins, each half of the diaphanous portion 

 being equal in breadth to that of the more solid part of the leaf itself, 

 and reaching farther up towards the top. Third, in the veil which 

 covers the macrosporangia being one half longer, leaving only one- 

 third of the spores naked. Fom-th, in the macrosporangia being 

 in more saccate cavities andfeiver in number. Fifth, in the smaller 

 microsporangia, which are nearly overlapped by the sheathing 

 bases of the leaf. 



Compared with I. setacea, Bosc, it differs, first, in being always 



N. s. VOL. 7. [December, 1878.] 2 z 



