Reactions of the Petioles of Pteris aqiiihna . 13 1 
flow, as in Fig. 3, iv, in which case the gummy deposit appears branched in 
a trirad iate or quadrate manner, as seen in transverse section. 
The discussion of the effect of wounding on the vascular bundles has 
been deferred till last, because it seems to have little or no connexion with 
Fig. 3. i. Diagrammatic transverse section of wound area, showing the cortical cells affected to 
an unusually large extent, ii. Tracing from i, indicating the ‘ lines of flow ’ exhibited by the 
elongated cortical cells and also the lines of contact, iii. Portion of ii, more highly magnified 
to show detail. This is from the left of ii. iv. Portion from the right of ii. Note the elongation 
of the endodermal cells at e. i and ii x 12, iii and iv x 300. 
the nature of the traumatic response in the general ground-tissue. The 
tissues 1 comprised in the vascular bundles show no reaction when the 
wound is purely superficial and does not penetrate the sclerenchyma. 
Apart from the occasional discoloration of the xylem and phloem elements, 
1 The endodermis is included here. 
K 2 
