158 



three sub-triangular portions. When crushed, even after the lapse of 

 years, these seeds are found to be filled with a transparent and some- 

 what oleaginous fluid. Other thecse contain apparent seeds, which 

 are extremely minute, being scarcely equal in size to the pollen-gra- 

 nules of many flowering plants : these minute bodies possess the form 

 and characters of the larger seeds. The thecae containing the two kinds 

 of seed are scarcely to be distinguished from each other, nor do they 

 follow any law in their relative position, as many of our botanists have 

 asserted, but most frequently occur alternately. Linneus, in his ' Iter 

 Scanicum,' has described these as male and female flowers, * but bo- 

 tanists are not agreed as to their precise nature, the question, when 

 discussed, must comprise the kindred twofold fructification of Lycopo- 

 dium Selaginoides, and probably many other species : the real nature 

 of the four portions into which each (supposed) seed is divisable, also 

 requires further investigation. I am too superficial a botanist to ofier 

 an opinion on so important a subject. 



Mr. Valentine, whose valuable paper on the structure and develop- 

 ment of the organs of Pilularia, in the 18th vol. of the Linnean Trans- 

 actions, has already been noticed in this work (Phytol, 55), has made 

 some interesting observations on the germination of Isoetes, which I 

 hope may eventually be given to the public. 



There are two forms of Isoetes, so difi"erent that Dillenius, and, in 

 some of his works, even Linneus, treat them as distinct species ; thus 

 in the passage quoted fi-om Dillenius, at p. 154, they are designated 

 "Subularia folio rigido" and "Subularia fiagilis;" and in his great 

 work, the 'Historia Muscorum,' the same author describes them as 

 "The short and thick-leaved Quillwort, Calamaria folio breviore et 

 crassiore," and "The long and slender-leaved Quillwort, Calamaria 

 folio longiore et graciliore ; " and enters very clearly into theh distin- 

 guishing characters.f The following paragraph from a letter of Lin- 

 neus to Haller, written in 1749 and printed in Smith's 'Selection of 



* Masculi Jiores solitarii intra basin foliorum interiorum. Cal. Squama cordata, 

 acuta, sessilis. Cor. nulla. Stam. Filamentum nullum. Anthera subrotunda, uni- 

 locularis, intra basin folii sita. 



Feminei Jiores solitarii in eadem planta, intra basin foliorum esteriorum. Cal. ut 

 in masculis. Cor. nulla. Pist. occultum. Per. Capsula subovata, bUocularis, intra 

 basin folii sita. Sem. numerosa, globosa. 



t Calamaria folio lougiore et graciliore. The long and slender-leaved Quillwort. 

 A precedenti differt foliis longioribus angustioribus et rectioribus: radix porro durior, 

 minus tuberosa, minusque crassa est et fibrae ejus breviores sunt et magis ramosae, cse- 

 teroquin foliorum texturam, colorem, semina et reliqua habet communia. Hist. Muse. 

 541, tab. LXXX. 



