790 



cambium and having at first the character of callus\ This holds good for 

 the products of division of the youngest bark, which united with the cambial 

 callus from the later overgrowth roll. 



At the time of girdling (in July) the old wood body of the vine (Fig. 

 183,//) was already strongly developed. We can recognize elongated, 

 thick-walled wood cells in the immediate proximity of the ducts (g), chiefly 



yr _.- 



S...-' 



Fig. 183. 



Long-itudinal section through an overgrowth roll which has developed 

 from the lower edge of the ringing wound (Fig. 182, u). 



provided with horizontal cross walls (h), otherwise usually pointed like -a 

 wedge and having fine pore canals (h'). The narrower vessels are spiral or 

 ring ducts (g) ; the wider ones show circular or slit-like pits (g). The 

 broadest of all have a ladder-like, or reticulated, porous wall. The ladder- 



1 All juvenile cicatrization membrane with apical growth of its cell rows, no 

 matter whether produced on a cut surface above or beneath the surface of the soil, 

 may be called "callus." "We will call the callus which has a bark, is lignified, and 

 continues its growth by an inner meristem zone the "overgrowth edge." 



