4 BULLETIN 1038, U. S. DEPARTMENT OF AGRICULTURE. 
dant cell sap and poverty of chlorophyll and partly to the smaller 
intercellular spaces. The thickness of the leaves is caused by the 
enlarged roundish sponge cells and by the massive, often transversely 
divided palisade. Sodium chlorid thus appears to act morphologi- 
cally, Warming says, in much the same way as sunlight (82). 
In the cell sap the solution of salt is more concentrated than in the 
soil. Side by side with this increased salt content goes a decrease in 
the development of chlorophyll, due to a reduction both in size and 
number of chloroplasts. Succulent halophytes usually show at first 
a dark-green color, later passing over into a yellowish green or red. 
Wax coatings are characteristic of many salt-loving plants. Some 
species, such as Solarium dulcamara Linn., are dimorphous, exhibit- 
ing halophytic forms and also inland forms with thin leaves. 
Such general environmental factors as those enumerated may and 
do have appreciable developmental results. Plants thrive or fail to 
thrive and may even die, or again various general adaptive morpho- 
logical changes are brought about, but there are no fundamental 
derangements in morphogenesis or in metabolism which could prop- 
erly characterize these conditions as disease. 
In this same category of general environmental effects are to be 
placed the calciphilous or lime-loving plants; and the calcifugous 
or lime-avoiding plants. Plants grown upon a lime soil, Warming 
says, tend to a greater pubescence and to a bluish green color and a 
more divided condition of the leaf (82). Moreover, not only are the 
chemical but also the physical characters of lime soils to be taken 
into consideration. 
It is but a step, now, from these general lime relations to some of 
the more specific lime effects usually considered as diseases. In the 
pineapple chlorosis of Porto Rico sometimes the plant becomes almost 
ivory white. In other cases the leaves are yellowish white with 
streaks or patches of green, or the outer leaves may be green while 
the later developing leaves at the center are white from the start. 
In still other instances the leaves, normally green for several months, 
may gradually develop a light-colored mottling until finally the 
whole leaf becomes blanched. The plants are dwarfed and the red- 
dish or pinkish fruit finally cracks open and decays. Gile (35-37) 
has definitely shown that this pineapple trouble is primarily caused 
by a lowering of the availability of iron to plant absorption due to 
calcium carbonate in the soil. A chlorosis of pineapple in Hawaii 
(46) appears to be caused by a similar depression of the availability 
of iron due to the high manganese content of the soil. 
Similar lime chloroses of rice and of sugar cane in Porto Rico have 
been shown by Gile and Carrero (38) to be caused by a lack of suffi- 
cient iron absorption. In all these cases spraying with a solution of 
