2 INTRODUCTION. 



each group in detail ; the tabular arrangement moreover is only a question of con- 

 venience ; we have not to deal with a directly ascending series of organic forms 

 which advance from the lower and simpler to the higher and more complex, but we 

 must rather conceive of the Vegetable Kingdom to use a frequent illustration as a 

 copiously branching tree, whose boughs have their origin in a common stem, but 

 stand in no direct communication with each other. We may then divide the 

 Vegetable Kingdom into the four following groups : 



First group : Thallophytes. 



Second group : Bryophytes (Muscineae). 



Third group : Vascular Cryptogams (PterLclophytes). 



Fourth group : Seed-plants (Spermaphytes). 



