FLORIDA STATE HORTICULTURAL SOCIETY. 
12? 
times calcium 1 , are not always present in 
sufficient amounts in an available form to 
supply the needs of the growing plants. 
Sulphur occurs in plant tissue in com¬ 
paratively small amounts. It is taken into 
plants in the form of sulphates, as potas¬ 
sium sulphate, calcium sulphate, and oth¬ 
er sulphates, and plays a very important 
part in the formation of albuminous mat¬ 
ter of plants. These albuminoids move 
about in the plant, principally towards 
the grain and fruit. In some plants sul¬ 
phur is a constituent of the essential oils 
and can be detected by the odor such as 
in the onion, garlic, horseradish and oth¬ 
ers. 
While iron is necessary for plant 
growth and is always present in plants, it 
occurs in about the smallest amount of 
any of the ash elements. The function of 
iron is to assist in the formation of chlor¬ 
ophyll or the green coloring matter of 
plants. It is not known yet whether iron 
enters into the chemical composition of 
chlorophyll or is merely associated with 
it.. 
Magnesium occurs in much smaller 
amounts than calcium does although it is 
stored up in the seeds about three times 
more liberally than is calcium. Magnes¬ 
ium assimilates more slowly than any of 
the other ash constituents of plants. It en¬ 
ters into the chemical composition of the 
chlorophyll although plants do not re¬ 
quire much magnesium until the period 
of formation of the seeds. It has been 
found that plants grown with an incom¬ 
plete supply of magnesium frequently 
have sterile seed. 
Calcium is always present in the ash 
material and plants cannot reach full ma¬ 
turity without it. In fact some crops, such 
as clover, peas, alfalfa, require so much 
calcium that they are called ‘dime 
plants.” The special function of calcium 
is in assisting in the construction of the 
cell walls, and no new plant cells can be 
formed without it. Calcium, is found in 
the leaves of plants at all stages of growth 
and is very essential for their full devel¬ 
opment. It has been stated that calcium 
compounds are necessary for the conver¬ 
sion of starch into cellulose. 
When the growth of a plant has been 
checked by withholding calcium, the 
plant will show increased vigor within a 
few hours after supplying it. Calcium un¬ 
like magnesium is assimilated in the early 
stages of the plant’s growth, for example 
in wheat 80 per cent, is assimilated before 
the plant heads. It does not accumulate 
to such an extent in the seeds as do- some 
of the other ash elements for only about 
i-io of the amount removed by grain 
crops is in the seeds, the remaining 9-10 
being distributed throughout the straw. 
It is probable that more work has been 
devoted to the study of nitrogen as a 
food for plants than to any other element. 
This is a specially interesting subject for 
the reason that plants are surrounded by 
an atmosphere of nitrogen and it was to 
determine whether it was possible for 
plants to use the nitrogen direct from the 
air. It has been found that there are only 
certain plants called legumes that have 
the power of utilizing this nitrogen for 
food by means of nodules or tubercles on 
their roots. Nitrogen is taken up by the 
roots of plants in the form of nitrates and 
combines with carbon, hydrogen and oth¬ 
er elements to form the nitrogenous com¬ 
pounds so largely present in plants. In 
the absence of nitrogen a plant makes no 
