182 LENTICULAR GLANDS. [BOOK n. 



constant in most plants, yet that it is not impossible that it 

 may be confined to roots growing in a resisting medium. 

 From the following experiments it will be seen that in Orchids 

 the root elongates independently of its extremity : On the 

 5th of August I tied threads tightly round the root of a 

 Vanilla, so that it was divided into three spaces, of which one 

 was seven inches long ; another four inches ; and the third, 

 which was the free-growing extremity, If inch. On the 19th 

 of September the first space measured 7-^- inches ; the second, 

 4-| inches; and the third, or growing extremity, 2^ inches. 

 A root of Aerides cornutum was, on the 5th of August, 

 divided by ligatures into spaces, of which the first measured 

 1 foot 3 inches; the second, 2^ inches; the third, 3-i- inches ; 

 and the fourth, or growing end, 1-^ inch. On the 19th of 

 September, the first space measured 1 foot 34- inches ; the 

 second, 2-f- inches; the third, 3^ inches; and the fourth, 

 4-| inches. 



Occasionally roots appear destined to act as reservoirs- of 

 nutriment on which those of the succeeding year may feed 

 when first developed, as is the case in the Orchis, the Dahlia, 

 and others. But it must be remarked, that the popular 

 notion extends this circumstance far beyond its real limits, by 

 including among roots bulbs, tubers, and other forms of stem 

 in a succulent state. 



By some botanists, and among them by De Candolle, it 

 has been thought that roots are developed from special organs, 

 which are to them what leaf-buds are to branches ; and this 

 function has been assigned to those little glandular swellings 

 so common on the willow, called lenticular glands by Guettard, 

 and lenticelles by De Candolle. Such swellings appear, how- 

 ever, to be in fact the commencement of roots, produced by 

 the first attempt of the woody matter of the longitudinal 

 system to become free and to quit the stem. 



Roots not only absorb fluid from the soil, but they have 

 been said to return a portion of their peculiar secretions back 

 again into it. Brugmans ascertained that the Pansy exuded 

 an acid fluid from its spongioles ; others found that various 

 Euphorbiaceous and Cichoraceous plants form little knobs at 



