332 Mr, Macleay on certain general Laws regulating [Nov. 



M. Fries, do not form one circle, but two ; one of Pileati, the 

 other of Clavati ; so that instead of the Tbjmenomycetes forming 

 four natural groups, viz. Sclerotiacei, Trcmellim, Uteriniy and 

 Hymeniniy they form, if our author be correct, five ; viz. Sciero- 

 tiacei^ TremeUini,* Vterini, Pileatiy and Clavati. 



But to understand this still better, we had as well perhaps 

 enter a little deeper into our author^s theory. Every group, he 

 says, which expresses well the character of the superior group 

 to which it belongs, is called the centrum ; by this, not meaning 

 the centre of a circle, but the site of the normal form or perfec- 

 tion of the particular structure common to the superior group, of 

 which it forms a part. The word perfection^ even as here used, 

 requires explanation ; for it does not, as might be supposed, in 

 this place signify affinity to any particular group. Our author, 

 on the contrary, most properly says, that the idea of perfection 

 in structure has nothing to do with affinity.f " Ipsa ha^c affini- 

 tas imperfectionem potius indicat ; perfectissima enim sunt in 

 quavis sectione ab omnibus aliis remotissima. Sic perfectissima 

 animalia et vegetabilia, quae maxime a se invicem remota ; infi- 

 ma, quorum hmites confluunt." Hence it follows, that the cew- 

 trum, or perfection of a group, is in fact that part of the circum- 

 ference of the circle of affinity w^hich is farthest from the neigh- 

 bouring group, and exactly the same thing with what in the 

 HorcR EntomologiceR has perhaps more happily been called 

 Type. 



Indeed the confusion arising from the use of the word centrum, 

 as applied to a point in the circumference of a circle, is still in- 

 creased by applying the word radii to those groups likewise in 

 the circumference which lead from one centrum or type to 

 another, and which 1 have termed annectent groiips.% The use 

 of these terms centrum and radii is the more unfortunate, as our 

 author never for a moment takes them in any other sense than 

 that in which I have used the expressions type and annectent 

 groups. When, therefore, he says that in every group, whether 

 class, order, &c. there are a centrum and radii, we must under- 



♦ This appears to be one of those interesting groups which connect the least per- 

 fectly organized beings with those which arc the most perfectly organized. In the de- 

 partment of Htisterophyta it is to the Coniomyceies or lowest Fungi, what in the animal 

 Idngdom the Vermes are to the Aciita. 



•f- To the general observations on this subject, as connected with the animal kingdom, 

 which I have given in Hora: Enlomologictc^ p. 205, I may add the botanical authority 

 of Prof. Schweigger. *' Nee etiam genera et ordines plantarum in lincam a cryptoga- 

 niicis ad dicotyledoneas progredientem ita disponi possunt, ut familia qujevis prasceden- 

 tis structuram magis evolutam praebeat. Vix ullus de vegetabilium serie usitata, a 

 cotyledonum numero deducta, affirmat, plantas dicotyledoneas omni ratione monocotyle- 

 doneis esse anteponendas." p. 6. De Plantarum vlassificationc nafurali Disquixitloni- 

 bus Anatomicis et Physiulogicis stahilicnda Commentatio, Auctorc A. F. Sc/iwciggcr, 

 4*c. Rcgiomonti IH20. 



t There arc several other terms used by I\I. Fries to designate his groups, and which 

 differ from those employed by me to express the nature of similar groups. Thus, his 

 intermediate genera are my osculant genera ; his subordinate genera are my types of 

 form or sub-gtnera, &c. 



