78 M. Brongniart on a Fossil Lycopodiaeean Fruit. 



spike, which, probably, like those of Selaginella, terminated 

 the branches. Here, therefore, we have a peculiar combina- 

 tion of characters, namely, sporangia analogous to those of 

 Isoetes united into a spike similar to that of the Lycopodiacege, 

 but much larger. 



The great size of these organs is, in fact, one of the striking 

 characters of these spikes ; it is in proportion to the arborescent 

 stature of the Lepidodendra, compared with that of the living 

 Lycopodiaceas, but it is none the less remarkable, for most 

 commonly the organs of reproduction do not follow the growth 

 of the vegetative organs : the largest tree ferns have sporangia 

 no larger than the smallest species, just as the flowers of our 

 largest trees are often even smaller than those of the humblest 

 herbaceous plant. In these plants of the primitive world 

 growth was simultaneous in both systems of organs. 



Thus the Lepidodendrece } or arborescent Lycopodiacege, had 

 spikes of fructification comparable in size to the cones of firs 

 and cedars, and containing very voluminous sporangia, even 

 larger than those of Isoetes, which they approach in form and 

 structure. 



A final question remains to be solved. Have the true Le- 

 pidodendra, the fruits of which, or Lepidostrobi, were investi- 

 gated by Dr. J. Hooker, only a single kind of spores ? or did 

 the imperfect state of his specimens prevent the recognition of 

 the nature of the spores contained in the sporangia of the 

 lower part of the spikes of fructification ? The form of the 

 spores of these Lepidostrobi, which is quite different from that 

 of the microspores of Triplosporites, would lead me to think 

 that these plants are not congeneric, and that the genus Tri- 

 plosporites of Robert Brown should be maintained. * 



The three known specimens of this plant do not establish 

 its real geological position ; the origin of that described by R. 

 Brown, and of that of the Strasbourg Museum, is entirely un- 

 known ; the one that I have just described was found in the 

 transported material of a valley in the Pyrenees, far from 

 the beds in which it must have been originally deposited ; 

 nevertheless we cannot doubt, from the nature of the plants 

 which it most nearly approaches, that it belongs to some bed 

 contemporaneous with the Carboniferous or Old Red Sandstone 

 formation. 



Robert Brown in his memoir has given no specific name to 

 the plant which he described ; but the confirmation of its ge- 

 neric value, and the probability that we shall find other forms 

 of the same genus, induce me to consecrate the memory of his 

 excellent observations by designating this species by the name 

 of Triplosporites Brovmii. 



