222 NOTICES OF BOOKS. 



kinds are then for perspicuity's sake collected together into groups 

 (ffreges). A systematic conspectus and a determining table at the 

 end of the book serve to facilitate the survey and the study of it : 

 a separate section determines the characters of the dried specimens 

 supplied from various collectors ; the most considerable collection 

 is that of Peter himself, consisting of 300 in number. 



Thus far we have been occupied with the systematic divisions 

 only, of value to the botanist especially ; the other divisions are 

 more generally interesting. First of all the morphology of the 

 various groups is treated of, their innovation, relations, and certain 

 biological characteristics indicated ; then the various points dis- 

 cussed bearing upon their behaviour under cultivation, those which 

 are constant distinguished from those which are variable, and so 

 forth. In the section headed "The species and its component 

 parts" it is shown that the kindred forms are of unequal systematic 

 value, and that the species consists partly of individual kindred 

 forms and partly of groups of them ; and an attempt is made to 

 explain in graphic demonstrations by means of divers examples the 

 phytogenetic origin of the kindred forms through variation and 

 divergence, and the influence exercised by the dying-out of them. 

 With regard to the systematic treatment of the subject, it is 

 affirmed that not all the kindred forms connected with each other 

 by intermediate links are to be considered as constituting a species, 

 because in that case the first and the last members of the series 

 would be less related to one another than to many others not con- 

 nected by kindred ties in cases where an hiatus occurs from 

 accidental circumstances, viz., extinction. 



The manifold relations of the series one to another are repre- 

 sented by several graphic illustrations. Further, an attempt has 

 been made to settle the manner in which the individual characters 

 have philogenetically developed themselves ; which of them are of 

 recent, which of earlier origin, thus indicating a pedigree, as it were, 

 of the Piloselloids. The multiplication of forms through hybrids is 

 particularly treated of ; and it is pointed out that in this way no 

 new phenomena are produced, but only new combinations of 

 characters already existent ; and that the kindred form conditions 

 are scarcely altered, because of their rare occurrence. For the 

 rest, the hybrids in the work before us are considered as inter- 

 mediate forms, and designated individually by name. The chapter 

 on geographical distribution will be read with especial interest, for 

 it is not confined to the Piloselloids, but gives us a sketch of the 

 origin of the Central European Flora in general. Particular 

 sections are devoted to the means for working at monographs, 

 literature, collections, travels, cultivation, method of work, and an 

 account of nomenclature. As the views of systematists with regard 

 to the systematic value of the kindred forms distinguished by the 

 authors may vacillate, a non-recurrent name has very properly been 

 given to every subspecies and important variety. 



Of course it is not every systematist who will coincide with the 

 ideas of species entertained by the authors. If the views of the 

 authors that the gaps between existhig species arc to be explained 



