to the Plant Cell. 
5 27 
plant growth, as some writers have done. Bruch (’02) has called attention 
to the fact that, aside from being unnecessary for Fungi and the lower Algae, 
it is quite toxic to certain swamp and aquatic plants. 
The analysis of a plant usually shows that the greater part of the 
calcium is deposited in the stems and leaves, which at least suggests that 
it is concerned with the synthetic formation or transportation of organic 
products. Calcium forms a relatively small part of the seeds and fruits 
of most plants. The amount of calcium in diseased or etiolated leaves 
is less than in healthy leaves. Smith (’93), in his studies of peach ‘yellows ’, 
gave the percentage of calcium in the ash of healthy leaves as 40 * 58 , and in 
the diseased leaves as 23 * 88 . In this connexion it may be proper to refer 
again to the results of von Portheim and Samec (’05). They found that in 
normal Phaseolus plants the amount of calcium was always greater than 
the magnesium, but that in etiolated plants the amount of calcium was 
often no greater than that of magnesium. All experimenters have observed 
that seedlings cultivated in solutions lacking calcium salts usually develop 
small leaves. 
When I cultivated Spirogyra in a nutrient solution lacking calcium 
the chlorophyll soon showed signs of injury similar to that described by 
Bokorny (’95) and Loew (’99). The lobate margins were lost, and the 
broad bands became narrowed to a mere line. During the first stages 
of injury the pyrenoids contained some starch, but as the chloroplast 
sustained further injury the starch was less distinct. After seven weeks the 
chloroplasts became vacuolated and disorganized. 
The chloroplasts of Zygnema likewise showed striking injuries when 
that alga was cultivated in a calcium-free solution. The delicate star-like 
form of the chloroplasts was lost because the radiating points were with- 
drawn. In cells which showed the most injury from lack of calcium 
the chloroplasts were contracted into irregular masses which ultimately 
became vacuolated. The application of iodine solution showed that 
each chloroplast contained considerable starch even when the injury was 
quite severe. 
After Spirogyra had been deprived of calcium for two months only 
the smaller part of the cells remained alive, and they showed marked 
indications of injury. I noted in such cases that the apical cell of a filament 
was generally the first, and often the only one to show evidences of injury. 
In addition to the injury to the chloroplasts, already described, I found 
that these cells were partly filled with a dark substance which rendered 
them more or less turbid. The accumulation of this turbid material was 
usually greatest in the vicinity of the nucleus. Marchi’s test showed that the 
substance causing turbidity was lecithin or some body closely related 
to the lecithins. 
In the majority of cases I failed to obtain much evidence which bore 
