1021 



imperfect that lie described the two parts of the archegonium, the 

 papilla and the enlarged emhryo-sac, as distinct structures ; while he 

 never traced the origin of the new pl9.nt at all. His observations may 

 therefore be safely passed over. Schachf s are more complete, but he 

 again only argues against the probability of a sexual conjunction, 

 with the preconceived notion that this must be analogous to what he 

 erroneously believes to be the conditions in the Phanerogamia ; while 

 his observations furnish facts which greatly support the probability of 

 an impregnation by the spermaiozoids ; the difficulties he suggests 

 being of little weight in comparison with those of accounting for the 

 existence of all the peculiar structures by any other hypothesis. 

 The opinions of all the rest are in favour of the impregnation (Thuret 

 does not treat of the arcJiegonia), and the differences between them, 

 except in the case of Suminski, are unimportant in a physiological 

 point of view, merely presenting questions of anatomical and morpho- 

 logical interest. And since Suminski's description of the mode of ori- 

 gin of the embryo would be altogether at variance with what exists, 

 not only in other plants, but also in animals, and is opposed to the 

 observations of all the rest of us (except the doubtful support given by 

 Von Mercklin), I cannot but repeat my belief that he was led from 

 the facts by his imagination being preoccupied by Schleiden's doc- 

 trine of the impregnation of the Phanerogamia." 



On Venation as a generic character in Ferns ; with Observations on 

 the genera Hewardia, J. Smith, and Cioyiidium, Moore ; bg 

 Thomas Moore, Esq., F.L.S., Curator of the Botanic Garden, 

 Chelsea. 



The object proposed by the author is to inquire — 1st, into the 

 general importance of modifications of the vascular structure of the 

 fronds in distinguishing the genera of ferns ; and 2ndly, into their 

 relative value in the cases instanced. He begins by referring to the 

 numerous authors by whom the venation has been turned to account 

 in the formation of genera or subgenera, and in particular to the 

 observation of Mr. Brown, that " for subdivision, the most obvious as 

 well as the most advantageous source of character seems to be the 

 modifications of the vascular structure, or the various ramifications of 

 the bundles of vessels or veins of the frond, combined with the rela- 

 tion of the sori to their trunks or branches." He notices an instance 

 in which Sir William Hooker has given generic importance to this 

 VOL. IV. 6 P 



