116 
FLORIDA STATE HORTICULTURAL SOCIETY 
other substances, which may be present 
in the soil. A concrete illustration is af¬ 
forded in connection with experiments 
which I made several years ago in Rhode 
Island. It was found that soil which had 
possibly never received any fertilizer 
treatment was exceedingly acid and con¬ 
tained substances so toxic to lettuce, spin¬ 
ach, beets, onions, asparagus, and many 
other crops, that they could not be grown 
successfully, and the application of a 
highly acidic fertilizer further accentu¬ 
ated the difficulty; yet other plants grew 
to perfection on this soil. I mention this 
merely as an illustration of the fact that 
we cannot conclude necessarily from the 
effect of a given substance or substances 
upon one kind of plant what the effect 
will be upon others. 
Question: What do you think of cot¬ 
tonseed meal as a source of ammonia? 
Answer: If you get meal which does 
not contain an undue amount of cotton¬ 
seed hulls, it generally has a fairly high 
availability, although it is not so quick in 
its action as the ammonia in dried blood, 
tankage, and dried fish. 
Mr. Beech: What can you say regard¬ 
ing calcium cyanamid? I am aware that 
it is considered to be destructive to plant 
nematodes. I also understand it carries 
a considerable amount of lime and that it 
should be applied some time in advance 
of the date of seeding. 
Answer: It is undoubtedly true that 
this material is destructive to nematodes; 
but in order to prove highly effective in 
this respect, it would have to be used in 
far greater quantities than should be rec¬ 
ommended in ordinary agricultural prac¬ 
tice, especially in view of its high content 
of nitrogen and lime. The material does 
have the advantage of supplying some 
lime, providing the plants grown and the 
soils used require it. It is also true that 
dicyanodiamid is formed from it when it 
comes in contact with moisture in the 
soil; and this material exerts a poisonous 
action upon plant roots until it, in turn, 
is decomposed by the micro-organisms 
and by chemical changes taking place 
within the soil. In general it should be 
applied two or preferably three weeks be¬ 
fore the seed is planted. It can be mixed 
with fertilizer in small quantities under 
such conditions that practically all of the 
nitrogen is transformed into urea, which 
is a most excellent source of ammonia for 
plants. Under other conditions of manu¬ 
facture, dicyanodiamid may be formed, 
so that here again the skill and experience 
of the manufacturer come into play. 
Calcium cyanamid has been found to be 
highly injurious to workmen who are 
brought extensively into contact with it 
in its natural state, especially if they have 
been imbibing alcoholic liquors. And I 
may add that I am not bringing this up as 
an argument in favor of prohibition, even 
in this dry city. 
Mr. Gray: Just a question in relation 
to bluestone. There are thousands of 
barrels of it used annually in this State; 
and in connection with your experiment, 
you show that the recovery of the trees 
was not necessarily due to bluestone. 
Where there are thousands of dollars at 
stake in connection with die-back, what 
would you advise a grower to do if the 
disease appears? 
Dr. Wheeler: I should by all means 
advise its use, until a time when some- 
