6 ENGLISH BOTANY. 



becoming hard ; bases of the lowest leaves containing macrosporangia, 

 and the upper ones microsporangia. Sporangia ovoid, about the size 

 of wheat or barley grains, immersed in the substance of the leaf to 

 which they are attached by the back, and more or less covered by a 

 membranous outgrowth from the margin of the fovea or depression 

 in the leaf termed the velum. Immediately above the fovea which 

 contains the sporangium, there is a transverse pit in the leaf termed 

 the foveola. The margin of this foveola nearest the sporangium is 

 elevated, and forms the labium, and from the bottom of the pit there 

 rises a membranous scale (lingule), attached by a broad base and 

 acuminated upwards. Macrospores -g 1 ^ inch in diameter, furnished 

 with prominent tubercles whose height does not exceed the breadth 

 of their base. The prothallium is formed at the apex of the macro- 

 spore, and eventually ruptures it, the macrospore opening by 3 sutures 

 corresponding with the converging lines at the apex. 



Var. /3 is a very remarkable form, and may be a distinct subspecies, 

 as which Dr. D. Moore has described it ; and in this view of it he is 

 supported by the authority of Prof. Caruel of Pisa, Prof. Duval-Jeune 

 and Martius of Montpellier, and Dr. Ascherson of Berlin, who all 

 consider it distinct from any described species. 



It is with great reluctance that I express an opinion different from 

 that of such great authorities, especially as I have not had an oppor- 

 tunity of seeing the plant in a recent state ; but the most careful 

 comparison of the specimens of I. Morei (which the late Dr. Moore 

 has kindly sent me) with those of genuine I. eu-lacustris leads me to 

 the conclusion that it is impossible to separate it even as a subspecies. 

 From the time of Dillenius it has been known that there are two 

 forms of Isoetes eu-lacustris, found growing in the same places, viz. 

 a solitary form in which the leaves are thicker, shorter spreading, and 

 more or less recurved, and another form, var. (3, Smith (Calamaria folio 

 longiore et graciliore, Dill.), a gregarious form, in which the leaves 

 are flaccid, longer, more slender, and more brittle. Modern British 

 authors regard these as states, and not varieties of the plant. Smith 

 advanced the untenable hypothesis that the tall and slender variety 

 might perhaps " be caused by those sudden risings of the waters so 

 frequent in mountainous countries." But as the stout recurved-leaved 

 plants grow in the same lake as the others, this is evidently a 

 fallacious idea. Mr. E. Newman no doubt has pointed out the true 

 cause of the variation of the plant, viz. that many of the spores 

 " remain in the capsule and there germinate, throwing up dense tufts 

 of slender leaves of a delicate green colour. I am indebted to Miss 

 Beever for specimens which beautifully exhibit this germination of 

 the seeds in situ, the parent plant and its offspring having been dried 

 while in the most favourable state for displaying this peculiarity, to 

 which Miss Beever particularly called my attention. These young 

 plants rapidly increase in size, send their roots downwards into 

 the earth, and their leaves upwards into the water ; and from the 



