10 
The chlorophyll in the leaves of normal pineapples is nearly all con- 
tained in this spongy parenchyma and is therefore protected from 
the direct sunlight by means of a layer of cells next to the epidermis 
containing a red coloring matter and by a layer of palisade tissue 
three or four cells deep. In Bromelia the palisade cells occupy 
about three-fifths of the thickness of the leaf and in Greigia about 
four-fifths of the leaf. The layer of delicate palisade cells, showing 
no cell contents except cell sap, makes it a rather difficult matter to 
obtain good free-hand sections without injury or disarrangement 
of the cell structure. The arrangement of the cell structures in the 
cross section of a normal pineapple leaf is shown in Plate I, A. 
In contrast with the anatomical features of the normal pineapple 
leaf attention is called to Plate I, B, which shows a corresponding 
section of a leaf of a pineapple grown on a highly manganiferous 
soil. This figure shows the destruction which has taken place in the 
chlorophyll and the protoplasmic bodies in, general. A few small 
green granules are observed here and there, but the most of the 
chlorophyll bodies have been disintegrated and have disappeared or 
at least lost their green coloring-matter. In a few instances it will be 
observed that the protoplasmic bodies have become discolored with a 
more or less pronounced brown. The arrangement of the chloroplryll 
bodies in the normal leaf is shown under higher magnification in the 
cells of spongy parenchyma in Plate I, C. If the condition shown in 
that figure is compared with A, B, and C of Plate II the stages in the 
disintegration and destruction of the chloroplasts will be readily seen. 
At first the chloroplasts begin to lose the regular form, and the green 
coloring matter is diffused through the protoplasmic substance of the 
cell, while the protoplasmic bodies disintegrate into smaller granules 
and remain separate or are grouped together in irregular masses show- 
ing a paler and paler green as the effect of the manganese continues. 
In the final stages of the yellowing of the leaf every trace of green 
matter has disappeared and only small irregular granules of pale 
protoplasm are to be seen in the cells which previously carried normal 
chloroplasts. The conspicuous feature of the effect of manganese 
upon the growth of pineapple plants is the pronounced and peculiar 
yellow color of the leaves. Under the microscope the cause for this 
yellowing is found in the loss of the green coloring matter and in the 
slight tendencv toward the vellowing of the cell wall and disin- 
tegrated protoplasmic substance under the influence of manganese. 
In the normal leaf an ordinary iodin test shows the presence of 
starch granules in the protoplasmic bodies. Simultaneous with the 
etiolation of the chloroplasts the iodin fails to show the presence of 
starch. In the later stages of the yellowing of the leaves only occa- 
sional granules of starch are to be found here and there in the dis- 
[Bull. 28] 
