CAUSE OF THE FORMATION OF BOOTS. 25 



in darkness and moderate moisture; that they are not, like 

 branches, the development of previously formed buds, but 

 appear fortuitously and irregularly from the woody rather than 

 the cellular part of a plant ; and that their production is in 

 some way connected with the presence of leaves or leaf-buds, 

 because portions of a stem having neither leaves nor leaf-buds 

 produce roots unwillingly, if at all ; and such roots perish 

 if their appearance be not speedily followed by the formation of 

 leaves. Thus although the first appearance of the root in the 

 embryo plant, at the time of germination, precedes the expansion 

 of the seed-leaves, yet the young root wUl not live unless the 

 seed-leaves are enabled to act. It is certain moreover that 

 their formation is greatly facilitated by the soil being warm, as 

 is sufficiently proved by the readiness with which they are 

 emitted by trees transplanted in August and September; as 

 also by the abundance of them in warm soU, and their fewness 

 and weak condition in soil not warmed by good drainage. 



It has beea remarked by a translator of this work that "the young 

 roots of some genera live for a very considerahle time without the 

 cotyledons exereisirig any functions. The seeds of the Pseony, sown in 

 January, will have formed roots in September, but the cotyledons ■will 

 not be visible for four or five months later, viz., in January or 

 February of the next year." 



But, although the immediate cause of the formation of roots 

 is unknown, the remote cause is apparently the elaboration of 

 organisable matter by the leaves ; for there can be no doubt 

 that the development of roots is much assisted by the descending 

 sap. When a ring of bark is removed from a branch, if the 

 wound is wrapped in damp moss, roots will invariably push 

 from the upper lip of the wound, while the lower will produce 

 none ; a fact so well known, that it has been one of the causes 

 of an opinion, that roots are bundles of wood liberated from the 

 central perpendicular system, and that the wood itself is nothing 

 but a mass of roots formed by the leaves and buds. 



The principal office of the root is to attract food from the 

 ground. For this purpose it is furnished, as has been seen, 

 with an extremely hygrometrical point or spongelet, which is 

 capable of absorbing incessantly whatever matter of a suitable 



