508 Notices of Memoirs — 



origins, whicli enable us to recognise community of descent in 

 existing groups between which a direct alliance is either dimly 

 suggested or absolutely unsuspected if we confine our investigations 

 to modern forms. 



Another fact that seems to stand out clearly is the almost world- 

 wide distribution of several characteristic Lower Carboniferous 

 plants. We are, as yet, unable to follow these Devonian plants to an 

 earlier stage in their evolution. We are left in amazement at their 

 specialised structure and extended geographical distribution, without 

 the means of perusing the opening chapters of their history. 



Upper Carboniferous (Coal-measures) and Permian Floras. — 

 The vast forests of the Coal age occupied an extensive area of land 

 on the site of the present United States of North America, stretching 

 across Europe into Eastern Asia ; under the shade of their trees lived 

 " the stupid, salamander-like Labyrinthodonts, which pottered with 

 much belly and little leg, like Falstaff in his old age." The plants 

 of these Paleeozoic forests seem to be revivified, as we subject their 

 petrified fragments to microscopical examination. Eobert Louis 

 Stevenson has referred to a venerable oak which has been growing 

 since the Eeformation and is yet a living thing, liable to sickness and 

 death, as a speaking lesson in history. How much more impressive 

 is the conception of age suggested by the contemplation of a group of 

 Palajozoic tree-stumps exposed in a Carboniferous quarry and rooted 

 where they grew ! An examination of their minute anatomy carries 

 us beyond the mere knowledge of the internal architecture of their 

 stems, leaves, and seeds ; it brings us into contact with the actual 

 working of their complex machinery. As we look at the stomata on 

 the lamina of a leaf of one of those strange trees, and recognise 

 a type of structure in the mesophyll-tissues which has been rendered 

 familiar by its occurrence in modern leaves, it requires but little 

 imagination to see the green blade spreading its surface to the light 

 to obtain a supply of solar energy with which to extract carbon from 

 the air. We can almost hear the murmur of plant-life and the 

 sighing of the branches in the wind as the sap courses through the 

 wood, and the leaves build up material from the products of earth 

 and air ; products that are to be sealed up by subsequent geological 

 changes, till after the lapse of countless ages the store of energy 

 accumulated in coal is dissipated through the agency of man. 



Time does not admit of more than the most cursory glance at the 

 leading types of the Permo - Carboniferous floras. The general 

 character of the preceding vegetation is retained with numerous 

 additions. Arcliceocalamites is replaced by a host of representatives 

 of the genus Calamites, an Equisetaceous type with stout woody 

 stems and several forms of cones of greater complexity than those of 

 modern Horsetails. Side by side with the Calamites there appear to 

 have existed plants which, from their still closer agreement with 

 Equisetum, have been described by Zeiller, Kidston, and others as 

 species of Equisetites. The genus Splienophyllum, a solitary type of 

 an extinct family, was represented by several forms which, like the 

 Galium of our hedgerows, may have supported their slender branches 



