218 BOTANICAL GAZETTE [MARCH 
it is not uncommon to find a thickened tissue lying next to the 
cell walls in the angles of the cells. In the more advanced stages 
of chlorosis the protoplasmic contents of pineapple leaves become 
contracted into formless masses and appear to undergo partial 
decomposition. Normally, the palisade cells (14) of this species 
contain not more than mere traces of chlorophyll, being essentially 
water-storage tissue. Under the influence of manganese the liquid 
content becomes coagulated and draws away from the cell walls; 
likewise the protoplasm in the chlorophyll-bearing cells breaks 
away from the cell walls in places, contracting into an irregularly 
shaped mass. Plasmolysis, therefore, takes place, and in a few 
instances the nuclei become brown. 
At the beginning of the chlorosis there is a fading of the green 
color without any other noticeable change; but in successive stages 
the chloroplastids gradually become fewer in number and smaller 
in size until finally they almost completely disappear. Simul- 
taneously with the fading of the chlorophyll, a diminution in the 
starch contents takes place, and as the chlorosis develops, less and 
less starch is found adhering to the chloroplastids, until finally it 
entirely disappears. In the chlorotic plants the palisade cells 
also seem to be given over to the storage of calcium oxalate, and 
the occurrence of this metabolic by-product is greatly increased 
in practically all parts of such plants. 
OXIDIZING ENZYMES.—The view that manganese exerts an 
influence on plants, through stimulating the auto-oxidations (so 
indispensable to living matter), gives interest to a study of the 
oxidizing enzymes occurring in plants from manganiferous soils. 
Accordingly, the oxidase and peroxidase activities of infusions 
obtained by crushing the leaves were measured empirically by = 
of the guiacum and aloin reactions. The results showed that while 
infusions from some chlorotic plants contain vigorous oxidizing 
enzymes, frequently such infusions give much weaker oxidase and 
peroxidase reactions than normal plants. These tests have been 
applied to infusions from all parts of pineapple plants, coming from 
soils containing manganese in amounts varying from 0.o1 to 9- 75 
per cent, and with plants at all ages and in the various stages in the 
development of chlorosis; but when applied to a large series of 
