LINDLEY'S NATURAL SYSTEM OF BOTANY. 5 



Ferns, Mosses, Mushrooms, and the like, neither flowers, nor 

 seeds properly so called, can be detected ; but propagation is 

 effected by the dispersion of grains or spores which are usually 

 generated in the substance of the plant, and seem to have 

 little analogy with true seeds. Hence the vegetable world 

 separates into two distinct groups, the Flowering and the 

 Flowerless. Upon examining more closely into the respec- 

 tive peculiarities of these two groups, it is found that flow- 

 ering plants have sexes, while flowerless plants have none ; 

 hence the former are called Sexual and the latter Asex- 

 ual. Then again the former usually possess a highly devel- 

 oped system of spiral or other vessels, w r hile the latter are 

 either altogether destitute of them, or have them only in the 

 highest orders, and then in a peculiar state : for this reason 

 flowering plants are also called Vascular, and flowerless 

 Cellular. More than this, all flowering plants when they 

 form stems, increase by an extention of their ends and a dis- 

 tention or enlargement of their sides ; but flowerless plants 

 appear to form their stems simply by the addition of new mat- 

 ter to their points ; for this reason, while the former are prin- 

 cipally Exogens or Endogens, the latter are called Acrogens. 

 Flowering plants are also for the most part furnished with 

 respiratory organs or stomates, while flowerless plants are to 

 a great extent destitute of them. No one then can doubt that 

 in the vegetable kingdom, two most essentially distinct divi- 

 sions exist, the Flowering and the Flowerless, and that these 

 differ not in one circumstance onh r , but are most essentially 

 unlike in many points both of organization and physiology. 



" In like manner, Flowering plants are themselves divi- 

 sible into equally well-marked groups. Some of them grow 

 by the addition of the new woody matter to the outside of 

 their stem beneath the bark ; these are Exogens : others 

 grow by the addition of new woody matter to the inside of 

 their stem near the centre ; these are Endogens. But Exogens 

 have two or more cotyledons to their embryo, and hence are 

 called Dicotyledons ; while Endogens have only one cotyle- 

 don, and are, therefore, Monocotyledons. Exogens have the 

 young external wood connected with the centre by medullary 



