722 



in all the genera, as it has already determined the presence of spiral 

 vessels even in those members of the class from which they were 

 originally supposed to be absent. But this is a matter of small mo- 

 ment in regard to the unity of the class, since the peculiarities of 

 the organs of growth among its members, in which they all seem 

 to agree, are sufficient to separate them from the phajnogamous 

 classes, with which other peculiarities in the organs of reproduction 

 indicate their affinity. 



One of Mr. Griffith's objections to the rhizogens, as a class, he 

 equall}' applies to gymnogens, viz., their inferiority in number of 

 species to the " other three natural classes or subkingdoms," allud- 

 ing to the exogens, endogens and acrogens (from which, when the 

 paper was written, the thallogens had not been separated). The re- 

 cently formed class, dictyogens, also agrees in this small number 

 of species. But this objection, so far from tending to overthrow the 

 claims of the rhizogens to a place as a separate class, ought, it seems 

 to me, to lead to the full recognition of those claims, and at the same 

 time, to the admission of the perfect applicability of Mr. Newman's 

 views of system to the vegetable kingdom. According to Mr. 

 Newman, as he has himself explained, the whole Animal Kingdom 

 naturally divides into four primary and three secondary (or minor) 

 groups. If really founded in Nature, equivalent groups ought to 

 exist in the other kingdoms as well as in the Animal Kingdom ; and 

 we accordingly find these groups ready made to our hand, and appa- 

 rently well defined, in Lindley's ' Vegetable Kingdom,' the latest and 

 best work on botanical classification published in this country. No 

 one will deny that the four primary groups are of higher value than 

 the three minor groups ; indeed, the inferiority of these latter, with 

 respect to the number of species included in them and other particu- 

 lars, is so generally understood, that this circumstance has even been 

 used as an argument against their admission." But when we consider 

 that Professor Lindley, without any reference whatever to Mr. New- 

 man's mode of grouping, has seen the necessity of separating the 

 gymnogens from the exogens, and the dictyogens from the endogens, 

 and has, moreover, from the internal evidence afforded by the rhizo- 

 gens, considered it necessary to retain that group entire, notwith- 

 standing the objections which have been raised to such a course; we 

 may, I think, safely allow that the formation of these three minor 

 groups was not altogether an arbitrary proceeding, but that there is 

 evidence of their being actually founded in Nature. 



