Physiological Studies in Plant Anatomy 129 
adjoining cells, and straightens out in the manner shown in Text- 
fig. 4. This separated strip is clearly the normal Casparian strip and 
under various treatments can be shown to possess its characteristic 
appearance and properties, as already described and figured (Text- 
fig. 2). But the separated cells still have their inner thick cellulose 
membrane surrounded by a continuous suberin lamella, staining 
brown with iodine reagents, so that by this method we have separated 
the Casparian strip from the suberin lamella. 
The difference between Casparian strip and suberin lamella is 
shown by their behaviour towards oxidising agents, and towards 
acids and alkalis. The Casparian strip is much more susceptible to 
the action of oxidising agents. Chromic acid or Schulze’s macerating 
fluid completely dissolves it in a few hours, leaving the long endodermal 
cells of the Potamogeton strips isolated in the macerating fluid. If the 
reaction is stopped in time, on treatment with iodine reagents, the 
suberin lamella can still be seen surrounding these isolated cells. Eau 
de javelle dissolves the Casparian strip more slowly but it disappears 
after three or four days from between some of the cells, and in other 
parts of the strip it appears thin and worn into holes, whilst the 
suberin lamella remains unaffected. 
On the other hand, the Casparian strip, as already shown, is 
extremely resistant to strong acids and alkalis. If the strips of 
tertiary endodermis are treated first with boiling concentrated potash, 
the suberogenic acids are removed from both the Casparian strip and 
the suberin lamella, leaving the Casparian strip regularly undulated 
and contracted as already described. But some basal substances 
must be left to the suberin lamella as the Casparian strip remains 
firmly attached to the inner cellulose wall, and the undulations of the 
Casparian strip are regular and of small amplitude. On now trans¬ 
ferring the strip to sulphuric acid after washing in water, the cellulose 
walls dissolve and also the remaining basal substance of the suberin 
lamellae, and the Casparian strip alone is left, much swollen and 
waved in the wildest fashion (see Text-fig. 5). These experiments 
seem conclusive evidence that there is a basal substance to the 
suberin lamella and that it is different from the basal substance in 
the Casparian strip, and thus we are presented with another unknown 
substance or class of substances. 
Provisionally it is suggested that it will be well to regard the 
basal substances of the suberin lamellae as somewhat resistant carbo¬ 
hydrates, akin to the inner carbohydrate lamellae of the tertiary 
stage. The work with Potamogeton has shown that these inner 
Phyt. XXI. III. 9 
