12 STEM. 



certain appendages of the stem to which the term root 

 is popularly applied. These are the tunicated and scaly 

 bulbs. 



63. These bulbs are spheroidal, laminated, or scaly 

 bodies, arising at the bottom of the stem just below the 

 surface of the ground, and from which, when separated 

 from the parent stem, a new individual is capable of 

 being produced. 



64. Tunicated bulbs are composed of concentric hollow 

 spheres laying one upon the other ; the inner spheres 

 are of a firm texture, whilst the outer ones are not. 

 They are seen in the Onion and Squill. 



65. Scaly bulbs have their pieces imbricated on each 

 other, the external ones being as firm as the rest. 

 They are seen in the Lily. 



66. All flowering plants possess, or have at one time 

 possessed, more or less of an ascending axis or stem ; 

 in some, however, this stem is not very apparent ; the 

 plant is then called acaulis. To the ascending axis 

 of Grasses and similar plants, the term culmus is ap- 

 plied, and to that of Palms, stipes. 



67. In considering the structure of the stems of 

 plants for the sake of convenience, and because it is 

 justified by high authority, we shall divide them into 

 three divisions, supposing that a distinct type exists for 

 each, and so examine the conformation of each division 

 separately, reserving for the physiological portion of 

 this subject the question of whether we are able to do 

 so with propriety. 



68. Stems may be divided into three kinds ; the Di- 

 cotyledonous and Exogenous, the Monocotyledonous 

 and Endogenous, and the Acotyledonous. 



Dicotyledonous and Exogenous Stems. 



69. On making a section of a stem of this division, 

 whose development is both mature and normal, (say of 



