568 Weiss . — The Vascular Branches of 
might be given of some of the tracheids in the outer cortex 
of the Stigmarian rootlet. Comparison might also be made 
with those plants which possess a more definite and restricted 
* transfusion tissue/ as defined by Mohl (VI). De Bary (’87) 
describes this transfusion tissue in the Conifers as ‘ attached to 
the xylem by means of one or two longitudinal rows of 
tracheids/ and as consisting of tracheids which ‘are on the 
average shorter and wider, and have terminal surfaces which 
are but little oblique, and may even be horizontal.’ This, too, 
would very fitly describe the tracheidal elements seen in 
Figs. 2, and 5 of the present paper. This comparison 
with the ‘ transfusion tissue/ in the restricted sense, receives 
additional weight from the fact that the leaves of the Lepi- 
dodendraceae possessed a considerable amount of transfusion 
tissue l y the cells of which resemble very closely the spiral 
tracheids in the rootlets of Stigmaria. A clear functional 
difference must, of course, have existed between these two 
very similarly constituted cells of the root and leaf of the 
Lepidodendraceae. The latter must have facilitated the out- 
ward passage of water in the leaf, whereas the former, if my 
interpretation is correct, must have accelerated the inward 
passage of water in the root. 
This would not be the only instance of similarly constituted 
organs acting in opposite ways in different parts of a plant. 
Indeed, the same organ may act both as a water-secreting or 
absorbing structure, as has been shown by Haberlandt (’95) 
and Von Minden (’99) in the case of the hydathodes of many 
leaves. The ‘ digestive glands ’ of insectivorous plants may 
be taken as a special instance of tfie double function of modi- 
fied hydathodes. 
A further support for the view I have advanced as to the 
probable function of the tracheidal patches of the outer cortex 
is gained from an interesting instance to which Professor F.W. 
Oliver has drawn my attention. Jonsson (’02), in his account 
of the germination of Agave 2 , refers to the occurrence in the 
1 Cf. Scott, D. H. (’00), Studies in Fossil Botany, p. 148. 
3 Cp. Jonsson, B. (’02), PI. Ill, Fig. 10. 
