572 



These were the avails of the rad'niJly divided zvood eells^ surronndimi 

 the ducts and containing starch which, therefore, niii/ht he more sensitiir 

 than the other elements of the vascular bundles. 



In frost Misters of the cherry, illustrated in Figs. 125 and 126. the 

 anatomical structure evidently differs from that of the frost blisters of the 

 maple branch, inasmuch as here the gummy exudation usually sets in as a 

 result of the injury. V\g. 125 is a cross-section tiirough the centre of a 

 blister. V\g. 126 a longitudinal section made at one side of the medial line 

 of the wound ; r is the brown stripe of dead tissue which immediately 

 bounds the inner, fine tear which caused the blister. This tear was not 

 visible externally since the outermost bark layers (c) had remained unin- 

 jured, although the wound was deep and extended to the old wood (h). 

 It must from the beginning have been very narrow, however, and produced 

 at a time when an immediate overgrowth was possible since the oxergrowth 

 tissue had sunk at once into the wound (r) witliout causing tlie death of 



m^^m^ 



^^t 



.1^ 



1 If, at the time of the awakening of vegetation, cross sections of Acer, Salix 

 viminalis, and other trees are treated with a strongly acid, concentrated .«oliiti()n 

 of c'liloriodid of zinc, large dark blue, variously shaped starch structures may ]>v 

 seen to pass out fiom these radially divided wood cells (compare Fig. 124 r). The 

 foi-ms of these are different. At times they may clearly be seen composed of sep- 

 arate, ii-regular, swollen starch grains because the cores, remaining firmer, appear 

 granular on the smooth upper wall surface of the pouch-like structure; they are 

 left after the dissolution of the peripherial layer of the starch grains. At times, 

 however, the substance of the hollow body is uniformly memljraneous and the upper 



surface smooth; the 



I til) often appears 



notched. In older wood 

 ^ such starch structure.s 



appear most numei- 

 ously in the autumnal 

 wood of the last two 

 annual rings. Glycerin 

 clears up the starch 

 pouches which occur 

 on the upper side as 

 well as the under side 

 of the section. Alcohol 

 l)iings out their con- 

 touis more sharply 

 and makes them seem 

 darker. P o t a s )i 

 bleaches them and 

 shows better the gran- 

 ular elements of the 

 walls. Their formation 

 seems to res-ult from 

 the swelling of the 

 starch gi-ains which 

 they rupture and, with 

 the reagent, transform 

 their contents into a 

 membrane in which, 

 at times, bright circu- 

 lar spots may V)e seen, 

 just as if vacuoles had 

 been deposited during the formation. The notched form of the tip is conditioni^a 

 by the irregular pushing forward of the individual, outermost starch grains. I 

 would like to consider these structures Traube's cells; strongly acid chlorzinc with 

 potassium alone showed a membraneous precipitate. Tin-chlorid (neutral) and 

 iron chlorid (acid) i)roduce no such structures. They are also not destroyed by 

 sulfuric acid or hydrochloric acid. A drying of the branches which had previously 

 displayed many such structures, decreases their formation or stops it entirely. 

 This phenomenon can not always be produced. It -seems to be connected with the 

 special constitution of the starch shortly before its dissolution in the early spring. 





•\,i30l/!Jp)^r<?'ooc/ 



'r 



Fig. 124. Starch structures formed in the treatment of 



sections of a young willow branch with chloriodid of zinc. 



They pass out of the bisected wood c'clls and often curve 



into the duct lumina. 



