ANOMALIES OF DEVELOPEMENT. CHAP. r. 



stem is made to descend every year into the earth. 

 The anomaly may be exemplified in the roots of 

 Vahriana dioica, Tanacetum vulgare, and Oxalis 

 acetosella ; and will also account for the bitten 

 and truncated appearance of Scabiosa succisa or 

 Devil's-bit. 



Anomaly The Beet root, a biennial plant, if dissected 

 root. when about a year old, presents the singular anomaly 

 of being already furnished with from five to eight 

 distinct and concentric circles of longitudinal tubes 

 or sap vessels, imbedded at regular intervals in its 

 pulp ; whereas other biennial roots form only an 

 individual circle each year, and are, consequently 

 at no time furnished with more than two.* 

 Migratory There are also some roots that may be called 

 migratory, upon a principle similar to the fore- 

 going. If the stem of a descending root happens 

 to be creeping or procumbent instead of being erect, 

 then the lateral shoots from above are carried for- 

 ward in the direction of that piocumbency, so that 

 in the course of a. few years the plant has actually 

 changed its place by so much as the stem has been 

 converted into a root. This is well exemplified in 

 the genus Iris. But the migratory plant is perhaps 

 best exemplified in the case of some aquatics, which 

 have actually no fixed habitat, but float about on 

 the surface of the water as they happen to be driven 

 by the winds, as in the case of the genus Lenina 

 and some marine plants. 



* Willdenow, p. 260. 



