308 . 



between the more anomalous forms of Cellulares and those of Flowering 

 Plants : I venture to do this with the more confidence, because the truth of 

 any opinions I may advance will have to be tried by the general layvs of 

 vegetable organisation, and upon principles which do not depend upon an 

 extensive acquaintance with species. 



We have seen that in Vascular plants the great divisions of Monocotyle- 

 dons and Dicotyledons, or of Endogenous and Exogenous plants, have been 

 satisfactorily establishe'd. In Cellulares attempts have been made to esta- 

 blish parallel divisions, but, I fear, without much success ; these plants 

 appearing to be analogous rather to one of the two divisions of Vasculares, 

 than to comprehend within themselves groups of equally different organisa- 

 tion. 



M. Decandolle refers Ferns and their immediate allies to Endogenous 



plants, and separates" the remainder into Foliacece, or plants with leafy ex- 



, pansions, and Aphyllce, or those destitute of leaves : but to the first of these 



there are grave objections ; the second nearly corresponds with the arrange-' 



ment here adopted. 



Agardh, in 1821, divided them thus: — Acotvledone.t,, or leafless 

 plants, with all the parts confluent, the colour not herbaceous, with no 

 sexes, and propagated by sporidia. (Sporidium est corculum nudum, radi- 

 cula, cotyledone, et hilo destitutum. Aph. 71.) Pseudocotyledone^, or 

 leafy plants, the parts of which are sometimes confluent, the colour green, 

 with an attempt at producing sexes, and propagated by sporules enclosed 

 in capsules. (Spora est corculum perispermio (?) et membrana simplici hilo 

 destitutainclusum, germinatione cotyledonidium (analogon cotyledoni folium) 

 explicans. Ibid. 71.) To Acotyledonese he refers only Fungi, Lichens, and 

 Algse, and comprehends the remainder in Pseudocotyledoneae. This arrange- 

 ment is undoubtedly natural, but it is liable to objection, on the ground, 

 that although the two groups are distinct, yet it is extremely uncertain whe- 

 ther the characters assigned to each are founded upon accurate observation. 

 For instance, the distinction drawn between their modes of reproduction or 

 germination is altogether arbitrary. It is well known that Mosses and Con- 

 fervse are so similar when germinating, that young plants of the former have 

 been described as belonging to the latter tribe (see Mr. Drummond's paper 

 in the Transactions of the Linneaii Society , 15. p. 20.); and yet one is said to 

 increase by sporules, and the other by sporidia. The confluence of all the 

 parts in Acotyledonese, and the separation of them in Pseudocotyledoneae, 

 will not distinguish them; witness Marchantia, Riccia, &c. in the latter, and 

 such species as Caulerpa hypnoides in the former. Colour is a still less 

 satisfactory difl^erence : for example, what green have we in Mosses or 

 Ferns, or other Pseudocotyledonea>, more intense than in Ulva and nume- 

 rous Algaj among Acotyledoneae ? As to a supposed tendency to deve- 

 lopement of sexes in one and not in the other, this may possibly be the 

 case ; but it is no character of the two groups ; for what better proof have 

 we of any such tendency existing in Lycopodineae or Hepaticai, than in 

 Lichens. 



Fries, in his Planter HomonemecE, adopts these divisions, but assigns 

 them new names and characters. He calls the Acotyledonesc of Agardh 

 Homonemea, and the Pscudocotyledonese he terms Heteronemea, with the 

 following characters: — Heteronemea. Germinating filaments, combining 

 in a heterogeneous body, with some analogy to the difference of sexes. 

 Tissue consisting of cellules regularly united. Homonemea. Germinating 

 filaments, either distinct or combining in a homogeneous body, with no trace 

 of sexual differences. Tissue consisting of anomalous, somewhat filamentous 

 cellules. — I scarcely know whether to consider these definitions more satis- 



