HISTORY OF PLANTS. 1/5 



found. All the powers pertaining to the cell seemed 

 to be fixed, for there is no reason for thinking that 

 the cells of early plants were not about like those of 

 to-day. During the Silurian also the stem and leaf 

 were differentiated. Sexual reproduction probably 

 had begun at this time, but it was in a low form, and 

 the formation of fruit did not appear until later. 

 Thus the advance has been almost wholly in refine- 

 ments of parts, and not in the productions of new 

 features. 



Finally, we notice that it is impossible at present 

 to trace the various types in the vegetable kingdom 

 to a common centre. We do not find any evidence 

 of a rapid divergence from one central point of origin. 

 In the animals we have reason for thinking that all 

 of the great types arose early as branchings from 

 one simple type, the Gastraea, and that the different 

 sub-kingdoms did not arise from each other to any 

 noticeable extent. In the vegetable kingdom the 

 reverse seems to be nearer the truth. New types of 

 plants were constantly arising till the Cretaceous, 

 and there is every reason for thinking that they 

 arose from the earliest existing plants in all cases. 

 In other words, the history of the vegetable world 

 is rather to be compared to the history of a single 

 sub-kingdom of animals than to the history of the 

 whole animal kingdom. Like the vertebrates they 

 have had most of their development since the Silu- 

 rian age, although it is true that their history really 

 began earlier. In the fossil history of plants, there- 

 fore, we find just such an advance as we have seen 

 in the vertebrates, and not such a mixture of ad- 



