10 INTRODUCTION. 



amongst each other in different directions, like the 

 meshes of a net work ; in species which run into 

 each other, and in varieties which aspire to the dig- 

 nity of species. Examples of this kind are the Com- 

 posite, the Umbel liferse, the Cruciferce, the Leg- 

 uminosse, the Grasses, etc., which form the delight 

 of the monographist, the despair of the universal 

 botanist. So we find that the fragmentary condi- 

 tion of a type, that is, the small number of species, 

 the well defined character of the genera, and the 

 absence of intermediate forms, is a peculiarity of 

 ancestral types but little changed from the forms 

 preserved in a fossil state. . Such a type, discon- 

 nected as it is, will show certain general affinities 

 with classes which in their living representatives 

 differ widely from them in the most essential parts 

 of their organization. For instance the Cycada- 

 ceoe, easily to be separated from their nearest rela- 

 tives the Conifers, exhibit analogies with the ferns, 

 among the Vascular Cryptogams, and the palms 

 among Monocotyledons ; classes now entirely dif- 

 ferent but evidently in times of which we possess 

 no fossil records, more nearly connected, and of 

 common parentage. 



The peculiarities of the modern types are the 

 direct opposite, for instance in Composite, Urn. 

 belliferre, Cruciferoe, etc., whose sharply defined 

 characters distinguish them clearly, leaving no 

 room for doubt or uncertainty to even the inexpe- 

 rienced observer. The greatest difficulty is found 

 in distinguishing the species and genera, which 

 seem to run into each other in all directions. 



