S54i ON A NEW SPECIES OF ISOETES FROM IRELAND. 



submerged ; second, in the corm being bilobed ; third, in the 

 leaves being without stomata ; fourth, in having the veil developed. 



In general outward appearance our Ii'ish plant bears more 

 resemblance to 7. setacea, Bosc, and I. Malinveniiana, DeNotaris, 

 than it does to I. lacustris. When laid side by side with strong 

 plants of 1. setacea, collected by Gay near Montpellier, and now in 

 the Kew herbarium, as well as strong plants in the herbarium of 

 the British Museum from several collectors, no difference is observ- 

 able, and even very little when the plants are examined under the 

 microscope. Out of five plants lately received from Professor 

 Martins of the Montpellier University, which had been grown in 

 rather deep water, one had the corm hilohed, another with a very 

 shght third lobe, and the leaves were destitute of stomata. The only 

 difference I could perceive between them and our Irish plant was 

 in the lingula and glossopode, the former being longer, more 

 transparent, with stronger margins, the glands on the glossopode 

 much clearer and better developed, besides the absence of the veil. 



Isoetes lacustris has been long known at Lake Bray, but only 

 the normal type, w^hich grows abundantly in the same lake along 

 with our present plant. Leaves of the latter have been picked up 

 by many collectors, but no definite opinion as to their belonging 

 to a distinct form seems to have been expressed until 1871, when 

 A. G. More, Esq., i^rincipal Assistant in the Natural History Museum, 

 Dublin, called attention to it in a paper read before the Eoyal Irish 

 Academy, which was reprinted, by permission of the Academy, as a 

 ' Supplement to Cybele Hibernica,' in 1872. In his observations on 

 I. lacustris Mr. More states, " A long slender form, some of whose 

 fronds measured twenty -six inches in length, is in autumn washed 

 ashore from deep water at Upper Lough Bray." On seeing the 

 leaves collected by Mr. More, it occurred to me that the plant 

 which produced them must be distinct from the ordinary state of 

 I. lacustris. It was not, however, until November, 1876, that I 

 obtained a supply of plants which were growing in situ. These I 

 brought to the Botanic Garden, and had them planted along with 

 plants of I. lacustris, where both preserved their respective forms ; 

 I, Morei producing long slender setaceous leaves, floating on the 

 surface of water, as they frequently do at Lake Bray ; I. lacustris 

 short stiff subfalcate leaves, remaining under water. 



Although our plant differs in so many particulars from the 

 normal state of I. lacustris, it may be only a remarkable abnormal 

 form of it. It is certainly much more distinct from it than 

 I. echinospora is, which differs in no essential particulars, farther 

 than the echinate macrospores and generally smaller more slender 

 setaceous leaves. 



It may be the fact that in Northern Europe we have only one 

 true species, I. lacustris ; I. ecliinospura and the present plant, 

 I. Morei, being the extremes of forms of that species '? However, the 

 parts which afford specific characters in this genus being so few, 

 and some of them, as we have seen, not very constant, it may be 

 taken for granted that the limits of true species of Isoetes are not 

 yet fully settled. But, either as a species or variety, I trust this 



