OF CENTRAL CANADA PART IV. 211 



argillaceous shales and in certain sandstones, usually in the form 

 of casts or impressions, with the surface coated with a thin layer of 

 black carbonaceous matter. 



The vegetable forms of existing Nature admit of a separation into 

 two primary subdivisions : Cryptogams and Phanerogams, or flower- 

 less and flower-bearing plants, respectively. In the latter although 

 in many of their types the floral organs are quite inconspicuous the 

 ovules or embryo seeds are produced and fertilized into seeds, 

 properly so-called, within the flower ; whilst in cryptogamic forms 

 there are neither flowers nor ovules, and consequently no true 

 seeds, but, in place of these, certain seed-like bodies, termed spores, of 

 a peculiar character. Some of the higher cryptogams, however, 

 notwithstanding these and other points of difference, make a close 

 approach in many respects to the lower phanerogamic types ; and it 

 is very probable that certain extinct forms of Palaeozoic vegetation 

 may have constituted connecting links between the two divisions. 



In each of these primary series, various subordinate groups are 

 recognized as shewn, in condensed form, in the following tabular 

 view : 



I. CRYPTOGAMS : 



1. THALLOGENS : 



(i.) Land Thallogens. 

 (ii.) Aquatic Thallogens. 



2. ACROGENS : 



(i.) Cellular Acrogens. 

 (ii.) Vascular Acrogens. 



II. PHANEROGAMS : 



1. GYMNOSPERMS : 



(i.) Cycads. 

 (ii) Conifers. 



2. ANGIOSPERMS : 



(i.) Monocotyledons, 

 (ii.) Dicotyledons. 



CRYPTOGAMS. 



CRYPTOGAMS, as already explained, comprise all flowerless forms of 

 vegetation, as lichens, sea-weeds, mosses, ferns, and the like. They 

 may be arranged broadly under two series : Thallogens and Acrogens. 



