72 



intcnupted from any cause, a circular an-angement vi the conseqixewc, — an 

 arrangement so conspicuous in the organs of the flower (61, ci, b, c), and in the 

 leaves of the Stellatae, and other plants. 



175. Wlien a single leaf arises at a node the arrangement is 

 more obviously spiral, and is said to hef alternate.^, "When tico 

 arise at each node they are placed opposite to each other, and at 

 right angles to the adjacent pairs. "V^Hien three or more arise at 

 each node they are disposed, of course, in a circle, and are said 

 to he verticillate, or whorled. 



176. In like manner,- the arrangement of the Lranches, when 

 divested of all disturbing causes,/is found to be spiral ; that is> 

 alternate in most plants, opposite in the ash, &c., or verticillate 

 in the pine, &c. 



^ \M\ 



FIG. 22. — 1, Buds, toriniiial and lateral, with their scaly envelopes ; 2, the scaly bulb of 

 !he lily, showing ils analogy to the bud ; 3, vertical section of the same. 



a. The ascending axis is exceedingly various in form, size, position, and struc- 

 ture, existing in every plant under some one or other of its modifications. It has 

 already been stated, that althongh its tendency is at first upwards, it does not 

 always arise above the surface. Hence the primary di-vision of this organ into 

 subterranean and aerial. 



111. The suRTERRANEAS STEMfwas deemed a root by the ear- 

 lier botanists, and those plants which possessed such stems only 

 were called acaulescejit or stcmless, terms still in use, denoting 

 merely the absence of aerial stems. The principal modifica- 

 tions are the bulb, corm, tuber, rhizoma, and creeper. 



