﻿576 Halsted : Starch Distribution 



ordinary leaf tissue strongly discolored by the iodine. It was also 

 seen with the lens that the blue color was not uniformly distrib- 

 uted, but in very narrow lines running parallel with the midrib and 

 corresponding with the smaller vascular strands in the leaf. 



If we turn now from the consideration of leaves infested with 

 fungi to stems that are similarly attacked the same rule obtains. 

 For example, some hypertrophied flower stalks of cultivated radish 

 that were in stock in formalin as student's material were thinly 

 sectioned and placed in a weak solution of iodine, when, within a 

 minute, the characteristic bluish tinge came into the sections. Sim- 

 ilar thin sections were made of the same stems, but at places where 

 no swelling or distortion had taken place and these showed but 

 the smallest amount of starch and that was usually in a single 

 ring of cells located just outside of the bast. As the bast is not 

 continuous the starch -bearing sheath so-to-say was likewise irreg- 

 ular and bent inward at the intervals between the bast stands. 

 There was practically no starch inside of this thin layer, but a 

 small amount outside of it. 



In the infested stems the starch is very abundant and in largest 

 amounts in the parenchyma, lying between the wedge-shaped bun- 

 dles and extending from them throughout the pith. Beside this 

 there is the starch-bearing layer above mentioned, but outside of 

 it there is no starch. The distribution of the oospores does not 

 seem to bear any relation to that of the starch. 



similar condition of things was met with in the hypertro- 

 phied stems {Exoascus sp.) of the wild goose plum {Pruniis hortu- 



lana Bailey) when compared with the normal parts of the same 

 twigs. 



The galls of the peach roots are simply gorged with starch, and 

 thin sections of them turn to a dark blue color. This color may 

 be brought out by cutting the knot through the middle and shaving 

 the surface smooth and applying iodine. Certain irregular layers 

 and folds will be darker than others, showing that the starch is dis- 

 tributed most abundantly around the wood proper and not in it. 



An interesting study in this direction was made of the cedar 

 galls of Gymnosporangium macropus Lk., where the starch is packed 

 away in the enlarged host cells to their utmost capacity, and thin 

 sections through the centers of large galls display a neat fan-shaped 



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