n 8 J. H. Priestley and Edith E. North 
Furthermore in thick macerated sections the endodermis will be 
found to flatten into a band in which it can be seen that cells vertically 
above one another also remain firmly attached, so that on both radial 
and transverse walls the middle lamella is untouched by these 
macerating fluids. We must now consider how the different behaviour 
of the middle lamella in these regions is related to the presence of the 
Casparian strip. 
(2) The Casparian Strip. 
Kroemer ( loc. cit. pp. 90-94) discusses the nature of the Casparian 
strip very fully. He concludes that the strip is formed of substances 
different from those composing the rest of the wall, and which are 
insoluble in concentrated sulphuric acid. These substances after 
treatment with eau de javelle are so altered that they are now more 
soluble in concentrated sulphuric acid than the remaining (cellulose) 
portion of the cell wall. 
Apart from the Casparian strip, the whole cell wall, both middle 
lamella and internal cellulose lamella, is directly soluble in sulphuric 
acid. If, therefore, sections of the young roots are placed in strong 
sulphuric acid the tangential walls completely disappear, so that the 
transverse appearance of the endodermis in section is as shown in 
Text-fig. 2 ( b ). All that is left are the Casparian strips, forming thin 
transparent wavy bands, staining yellow in iodine, very difficult to 
see in section, usually appearing either as a flattened ribbon with 
occasional pleats as seen from the side, or a dark triple line as seen 
