RHIZOMES. 



6i 



obliquely from the shoot-axes, as is generally the case, they produce numerous roots. 

 I could scarcely mention a more illustrative example of Rhizomes or Root-stocks 

 than those of the genus Iris, the Flag {Acorus calamus), and especially the common 

 Asparagus {Asparagus officinalis). The examples named, moreover, offer only 

 a small selection from the great variety of subterranean forms of shoot. It is for 

 our purpose, however, quite superfluous to enter further into particulars, since any 

 one who has rightly understood what has been said will, on careful observation 

 of any subterranean shoot, easily comprehend the true state of the matter. Con- 

 cerning this, I may simply remark that one has to guard occasionally against 

 confounding subterranean shoots with roots; since the former very often assume 

 externally the aspect of roots. Above all, they contain no chlorophyll : the sub- 

 terranean shoot-axes are white, brown, or yellow, instead of green. The decisive 

 point always lies, however, in that subterranean shoot-axes possess leaves, and bear 



Fig. ^.—Polygonatum muUiflorum. The anterior piece of a much longer rhizome, consisting of 

 four annual growths, A seen in profile, B from above ; all the adventitious roots have been cut off, their 

 position being indicated by the roundish scars. The numbers 1864, 1865, 1866, indicate the years in 

 which the respective pieces of the sympodium have been produced. 



a leaf-forming bud at the end. Of course the leaves of runners and rhizomes are 

 usually small, inconspicuous, membranous, or scale-like, and arrested generally, 

 since the true leaf-nature can only appear when the leaf nidiments develope under 

 the influence of light as green foliage leaves. That these inconspicuous sub- 

 terranean leaves, like the scales of sub-aerial winter buds, are only arrested 

 foliage leaves, may be in part experimentally demonstrated ' ; since it is possible, 

 by proper interference with the normal conditions of vegetation, to produce true 

 foliage leaves from such scales. With respect to Bulbs, it may finally be mentioned 

 that their stout, soft scales are also leaves, according to their developmental history 

 — generally entire metamorphosed leaves, as in the Crown Imperial and Tulip. 



^ That the leaf-scales are only foliage leaves prevented from their normal development, but do 

 not represent a so-called leaf-formation in the sense of the Braunian Morphology, has been 

 experimentally demonstrated by Goebel, Bot. Zeitg. 1880, pp. 7:3, &c. 



