132 Notices of European Herbaria. 



British Museum, I found precisely the same mode of struc- 

 ture to prevail. The horny fibres were completely enclosed 

 in a fleshy or cellular structure, in which numerous slender 

 siliceous spicula were imbedded. 



From the nature of the structures exhibited in both of 

 these keratose* sponges, and the prevalence of siliceous spicula 

 in such abundance in the fleshy or cellular structure which 

 surrounds the horny fibres, there is very strong reason to 

 suspect that the fibre of the sponges of commerce will prove, 

 in its natural state, to be surrounded by a similar fleshy mat- 

 ter, and that spicula will be found in a like manner to those 

 I have described as existing in the two species mentioned in 

 this paper. 



DESCRIPTION OF THE PLATE. 



Fig. 1. The sponge of its natural size. 



Fig. 2. The interior of tlie sponge, as seen with a power of 120 linear ; a, 



the horny fibre, surrounded by the fleshy substance ; b, b, spicula 



imbedded in the fleshy substance. 

 Figs. 3, 4, 5 and 6. Various forms of spicula found imbedded in the fleshy 



substance of the sponge. 

 Fig. 7. A view of the cuticle of the sponge, as seen with a power of 120 



linear. 

 Fig. 8. A view of the interior of the sponge, with the gemmules imbedded 



in the fleshy substance, seen with a power of 120 linear. 



XVIII. — Notices of European Herbaria, particularly those 

 most interesting to the North American Botanist^. 



The vegetable productions of North America, in common with those 

 of most other parts of the world, have generally been first described 

 by European botanists, either from the collections of travellers or 

 from specimens communicated by residents of the country, who, in- 

 duced by an enlightened curiosity, the love of flowers, or in some in- 

 stances, by no inconsiderable scientific acquirements, have thus 

 sought to contribute, according to their opportunities, to the promo- 

 tion of botanical knowledge. From the great increase in the number 

 of known plants, it very frequently happens that the brief descrip- 

 tions, and even the figures, of older authors are found quite insuffi- 

 cient for the satisfactory determination of the particular species they 

 had in view ; and hence it becomes necessary to refer to the herba- 

 ria where the original specimens are presers^ed. In this respect, the 

 collections of the early authors possess an importance far exceeding 



[* The term keratose seems objectionable, though sanctioned by authori- 

 ty ; since ose is not a proper termination for adjectives from the Greek ; 

 and analogy would require the x in Ki^ot-g to be expressed by a r, as in cen- 

 taur, not kentaur, &c. Would not ceratine, or corneous, be better? — Ed.] 



\ Conunimicated to Silliman's American Journal by the Author, pro- 

 bably Dr. Gray. 



