598 



their individuality, and becoming blended in all their parts with their 

 fellows, until almost all trace of their real origin is lost. 



" This is the substance of the doctrine of Morphology, the most 

 important generalization in the whole science of Botany, as affording 

 a clear and systematic view of the vegetable kingdom as a whole (in 

 addition to the important relations it establishes with Zoology) ; this 

 general statement is as much as can be indicated at the present stage 

 of the subject, the proofs and elucidations of the theory being those 

 very facts to which the greater portion of the following pages will be 

 devoted. 



" The presence or absence of the middle portion or stem of the 

 typical phyton characterizes the most important distinction in the 

 condition of plants, and on this ground the primary divisions are es- 

 tablished. 



" Plants which have no axis, but consist of cellular expansions, 

 are called stemless plants. The filamentous or foliaceous expansion 

 is called a thallus, from whence the division has received the name 

 of Thallophytes. 



" Plants which possess an axis or stem interposed between the 

 leaves and roots, either simple or compound, are called Cormophytes." 

 —p. 47. 



Chapter V. treats of the Axis and its Appendages : the first section 

 describes the structure of stems, giving a separate consideration to 

 Acotyledonous Stems, Monocotyledonous Stems, Dicotyledonous 

 Stems, Ligneous System and Cortical System. The second section 

 describes the root, and after a few general considerations we have the 

 following detailed account of the root in the three different classes. 



" Acotyledonous Roots. — The simplest form of the roots of this class 

 are mere cellular fibrillae, which supply the young stem with nourish- 

 ment. When this has become developed it gives origin to adventi- 

 tious roots ; that is, the radicle merithal of each phyton becomes free. 

 Roots are usually produced all round if the stem be erect, or on the 

 lower side if the stem be horizontal. 



" In the arborescent ferns these adventitious or free roots accumu- 

 late in such numbers that the base of the tree becomes increased in a 

 conical form to two or three times the thickness of its real stem, 



" The roots of these plants correspond in the nature of their ele- 

 mentary stnictures to the stems from which they grow ; cellular in 

 the cellular plants, as the mosses ; in the Lycopodiaceae and ferns, 

 &c., they contain fibro- vascular bundles. These bundles, however, 

 are generally central in the roots, enveloped in a layer of parenchyraay 



