545 



monium, is to be considered as a secondary infection, just like the almost 

 omnipresent Cladosporium. 



If now the injured spindle is examined in those places which Acre- 

 monium has not infested, the pictures reproduced in Figs. 115 and 116 are 

 obtained. Fig. 115 represents a cross-section through an internode; Fig. 

 116, one through a node of the head spindle; c indicates the epidermis; h, 

 its hairs ; g, a healthy vascular bundle ; </', a bundle with shrivelled brown 

 walls; gs, vascular bundle sheath; h, bast parenchyma; kg, wood part of 

 the bundle ; u, deep brown tissue between the two large ducts, which is very 

 sensitive and is proved to be injured first by various causes; pr, healthy 

 prosenchyma cells; pr' , the same with healthy walls but brown, filled lumina; 





.^'< 







pr 



Fig. 116. Cross-section through the node of the sterile stalk. 



pr", prosenchyma possessing colorless cell cavities but deeply browned walls ; 

 v, parenchyma cells in the epidermis and bark tissue with yellow, thickly 

 swollen walls and barely distinguishable lumina ; .::, elongated cells near the 

 gum-like, swollen tissue centres; bl, basal part of a head which separates 

 here from the node. 



Thus, in the bare parts of the head spindle, all those forms of injury 

 are found, which are noticeable in the lower nodes of all frost-injured 

 grains, only, instead of clefts in the tissue, swellings of the membrane pre- 

 dominate. These are especially extensive at the places of attachment -of 

 the heads because much more abundant parenchyma tissue, i. e., tissue more 

 susceptible to frost, is present there. And such gum-like, szvollen tissue 

 centres lie deep in the interstices of the spindle. By means of this ana- 



