170 PHILOSOPHICAL NOTES ON 



From all this it would seem that there is no essential distinction 

 between the stem and the root. One is a prolongation of the 

 other. They appear to be both off-shoots or sub-divisions of the 

 common cellular and original placenta-Hke organs of seaweed 

 fronds — the disk of attachment. The roots of phtenogams now 

 do for land plants a great deal of what the fronds alone did for 

 many seaweeds. 



The study of the roots of terrestrial orchids, as shown in 

 Syme's " British Botany/* will not leave us much to desire in 

 support of the notion that the stem and root are essentially one 

 thing. 



Some of the roots of these orchids become arrested, and swell 

 out, as storage roots, as in Orchis and Ophrys, while the remaining 

 roots function as roots proper, but which Syme calls stolons * In 

 some cases, at the extremity of the root, a small storage tubercle 

 (really a terminal bud) is formed, as in Herminium monorchis. 

 In others, most of the roots become enlarged. 



In Epactitis latifolia, the only roots are those given from an 

 underground stem with bracts on it, from the sides of which the 

 roots emerge, exactly as the aerial roots do in many orchids, from 

 the ^-icinity of the leaves. In Epipogum apliyllum the roots branch 

 like those of CoraUorhiza^ " but the branches have a few small 

 scarious scales,^' observes Syme. The most convincing of all are 

 the roots of Neottia Nidus-avis, which has its root-stock " densely 

 closed with thick cylindrical pale fawn-colour simple root-fibres, 

 from the point of which it is stated new plants are produced. 

 (See Leight, " Fl. Shrop.," p. 434.) 



It is next to impossible to study these terrestrial orchids, and 

 not be convinced that the stem and the root are one continuous 

 organ, the two di\'isions of which are adapted to two different 

 media. 



We might, therefore, regard the sub-divisions of the roots of 

 plants as underground leaves, devoid of mesophyl, which is not 

 needed, owing to darkness. On the other hand, leaves might be 

 considered as above-ground roots. In the latter the meso- 

 phyl (a tissue evolved in connexion with light) has developed, 

 and fasciated the veins of the leaf, which are homologous with the 

 root fibres of the roots proper. Or, we might look upon the leaf- 



* If these stolons are not roots, then these ground orchids are rootless. 



