adverting to the late Mr. Griffith. 379 



RHIZOGENS. 



87. More recently, Mr. Griffith has adopted the views of Brown, 

 and endeavoured by new arguments, to show that Rhizogens cannot 

 be regarded as a peculiar class in the vegetable kingdom. He is of 

 opinion, that " in the construction of the group, a remarkable diver- 

 sity of characters has been sacrificed to an appearance resulting from 

 parasitism on roots, and to an assumed absence of an ordinary form 

 of vegetable embryo." He asserts, that these plants are not similar 

 in their parasitism, and that in those which he has examined there 

 would appear to be two remarkably different types of development of 

 the embryo. He thinks, moreover, that such a class is opposed to 

 the system of nature, a chief point of the plan of which consists in 

 an extensive interchange of characters, either positively by structure, 

 or negatively by imitation of structure. The want of uniformity in 

 opinion of the founders of the group regarding its rank or value, is in- 

 compatible with any group of the system of nature. And he is 

 persuaded that Rhizogens are an entirely artificial class, not even 

 sanctioned by practical facility, which is the only merit of an arti- 

 ficial association, and a retrograde step in the course of philosophi- 

 cal botany. This being the case, it was of course necessary to 

 show where the genera of Rhizogens can be stationed, if they are 

 not collected into one common class, as is here proposed. Accord- 

 ingly, Mr. Griffith suggests, that the genus Mystropetalon may be 

 " the homogeneous-embryo-form of that order which he takes to 

 include Proteaceae, Santalacese, &c. and which nearly agrees with Pro- 

 fessor Lindley's alliance Tubiferse." The tendency of Sarcophyte is, 

 he thinks, towards Urticacese, and he also considers Balanophora 

 as the homogeneous-embryo-form of Urticacese, forming a direct 

 passage in one, and usually the more perfect structure of Musci and 

 Hepaticse. " Finally, he stations his genus Thismia between Tacca- 

 cese and Burmanniacese." (Proceedings of the Linnsean Society, 

 No. xxii. p. 220.) 



APOSTASIACE^l. 



184. Perennial herbaceous plants; stem simple or branched. Leaves 

 firm, thin, sheathing at the base. Flowers in simple or compound 

 terminal racemes. Calyx and corolla each consisting of three similar 

 pieces. Anthers two or three, sessile upon a short column, erect 

 2-celled, opening longitudinally; pollen cohering in 3s. or 4s. ac- 

 cording to Mr. Bauer, in single oval grains with a longitudinal furrow 



