T. D. MosscROP 179 



4 gm. calcium cyanamide in a crucible, mixed in one case with water, in 

 another with damp soil, and in the other with soil-water to ascertain 

 whether the soil bacteria would affect the matter. In no case was the 

 calcium cyanamide or any Uquid from it allowed to come into contact 

 with the seeds. In the control twenty-two seeds had germinated by 

 the fifth day but those in the other bell-jars soon darkened and were 

 black by the fourth day. Microscopic examination showed that whilst 

 the testa (seed-coat) was uninjured the cotyledons were blackened and 

 completely disorganised. Both the water and air in these three jars 

 were strongly alkahne at the end of the test. Some lettuce seeds were 

 then immersed in bench ammonia for a few hours, the same blackening 

 and disorganisation of the cotyledons following. Fresh seeds and tiles 

 were then used and dilute ammonia was put in the crucible. The 

 seeds blackened in 24 hours and none germinated. Similar tests were 

 then undertaken with one gram of calcium cyanamide and turnip and 

 barley seeds, but apparently the ro buster seeds were able to withstand 

 the smaller quantity of calciimi cyanamide as there was very httle 

 difference in the germination. 



Under certain conditions — generally of storage and non-bacterial 

 decomposition — there may be formed from calcium cyanamide, 

 cyanamide CN . NHg , dicyandiamide C2N4H4 — a polymerisation pro- 

 duct, and cyanamide carbonate. All of these compounds are stated to 

 be distinctly toxic. The polymer is fairly stable and does not produce 

 ammonia on distillation with magnesia. It is also extremely unHkely 

 to be formed under the conditions existing in the soil. Cyanamide and 

 its carbonate are rather different and might conceivably be formed as 

 intermediate products. Now cyanamide itself is, when pure, a sohd 

 melting at 40° C. But it is usually separated from its solutions as a 

 liquid and is described as volatile in steam, i.e. it has an appreciable 

 vapour pressure. As it forms salts with alkalies it is reasonable to 

 suppose that, if formed, it would combine with the CaO in the fertiliser, 

 but it was deemed advisable to set the matter beyond doubt by further 

 experiments. Accordingly ten seeds each of lettuce, swede turnip and 

 wheat were placed on tiles under bell-jars under the following conditions : 



No. 1 was the control. 



No. 2 contained a crucible in which were 2 gm. of calcium cyanamide 

 and water, the crucible being tied over with filter-paper soaked in NaOH 

 so that if cyanamides were formed they would combine with the NaOH. 



No. 3 was the same as No. 2 but the filter-paper was untreated. 



No. 4 was furnished with a crucible containing 2 gm. (NH4)2 SO4 



