12 VEGETABLE ORGANOGRAPHY. 



spikelets are arranged in spikes, as in the Wheat, and 

 that they are paniculate when they are in a panicle, as 

 in the Millet and Agrostis. * 



The Spadix is also a kind of spike to which a par- 

 ticular name is given ; it is applied to the spike of 

 Monocotyledons, when they are enveloped in their 

 young state by a large sheathing bract, which com- 

 pletely surrounds them, and is called the Spathe. The 

 spadix is simple, in Arum, for example, and sometimes 

 it is covered with flowers throughout its whole length, as 

 in Calla; at others its summit is naked, as in Caladium : 

 it is branched in the Palms. 



Besides these modifications of the structure of spikes, 

 to which it is thought fit to give particular names, they 

 also differ from one another: — 1st. In the distance of 

 the flowers, or the length of the internodes ; thus, the 

 flowers are very close in Plantago lanceolata, and very 

 distant in P. sparsiflora ; frequently the lower ones are 

 more distant than the upper (spica basi interrupta). 

 2d. In the relative position of the flowers : opposite, as 

 in Crucianella ; verticillate, as in Myriophyllum ; disti- 

 chous, as in Gladiolus ; or in a simple, double, or mul- 

 tiple spire ; characters always connected with the 

 disposition of the leaves. 3d. In the size and nature 

 of the bracts ; when these are large and foliaceous, the 

 spike is leafy (spica foliosa). 4. In the form of the 

 central axis, or rachis ; which may be cylindrical, com- 

 pressed, angular, or marked with depressions, in which 

 the flowers are as it were inserted. 5. In the general 

 form, which is usually cylindrical or conical, but some- 

 times oval or globular, and then it may be confounded 

 with the capitate flowers, of which we shall afterwards 

 speak. 



2d. The Raceme (racemus) only differs from the 

 ?pike in having longer pedicels, arising from the axils 



