NA TURE AND HABITS OF ORCHIDS. 29 



It is not alone in the form of the flowers that the Orchi- 

 daceous plants differ from other members of the floral 

 world ; the tt hole structure of the plant is peculiar. The 

 roots are of four kinds. First, annual fibres, simple or 

 branched, of a succulent nature, incapable of extension, 

 and burrowing under ground, as in the genus Orchis. 



Secondly, annual fleshy tubercles, round or oblong, 

 simple or divided, as in the various species of the same 

 genus ; they are always combined with the first, and ap- 

 pear to be intended as receptacles for matter fit for the 

 nourishment of the plant. 



Thirdly, fleshy simple or branched perennial bodies, 

 much entangled, tortuous, or irregular in form, as in 

 Corallorhiza, or nearly simple and resembling tubers. 



Fourthly, perennial round shoots, simple or a little 

 branched, capable of extension, protruded from the stem 

 into the air, adapted to adhering to other bodies, and 

 formed of a woody or vascular axis covered with cellular 

 tissue, of which the subcutaneous layer is often green and 

 composed of large reticulated cells. 



The stem is often (as in some terrestrial species) merely 

 a growing point surrounded by scales, and constituting a 

 leaf bud when at rest, but eventually growing into a 

 secondary stem or branch on which the leaves and flowers 

 are developed. In other cases the growing point becomes 

 perennial, thickens, is scarred with the remains of leaves 

 which once grew upon it, and assumes the state of a 

 short, round, or ovate perennial stem or pseudo-bulb. 



Or again, the rhizoma, instead of having pseudo-bulbs, 

 forms short stems which are terminated by one or more 

 leaves. 



The leaves are very uncertain in their appearance; 



