to the Plant Cell. 
505 
investigator appears to have discovered, incidentally, that calcium salts 
have a stimulating action upon root growth. It has since been shown that 
other salts will produce the same effect, but Wolfs discovery appears as 
one of the first attempts to explain the unknown but beneficial action of 
calcium salts on certain soils. 
Holzner (’67) assumed on very insufficient grounds that calcium salts 
are necessary for the formation of cellulose. He regarded calcium as the 
carrier of phosphoric and sulphuric acids in the plant, and believed that 
these acid radicals were replaced by that of oxalic acid when they reached 
cells in which proteid synthesis occurred. We have evidence now that 
this latter assumption must be regarded as untenable. G. Wolf (’68) first 
showed that the functions of calcium in the plant could not be performed 
by magnesium. Stohmann (’62) demonstrated the necessity of calcium in 
the formation of the green parts of the plant by cultivating corn plants in 
solutions lacking calcium. At the end of five weeks the plants were dead 
at the tips ; after the addition of a small amount of calcium salts, the plants 
quickly took on new life and began forming new leaves and shoots. 
Boehm (’75) seems to have been the first to discover any of the more 
important functions of calcium. He observed an abnormal accumulation 
of starch in plants ( Phaseolus vulgaris) grown in water cultures lacking 
calcium ; the accumulation of starch being in the pith and cortex of the 
lower part of the stem of the plants. He also found that calcium is 
necessary for the formation of new cell walls, although his idea of the 
mode in which calcium functions in cell-wall formation was probably 
incorrect. He believed that the function of calcium in the formation of 
cellulose walls was similar to its action in the formation of bone in animals. 
It was demonstrated by Molisch (’95) that this conception of the action of 
calcium was erroneous. Molisch showed that transverse walls in Spirogyra 
did not develop, or consisted only of imperfect septa when calcium salts 
were lacking, and that there was a non-formation of all parts. Boehm 
also found that the addition of calcium salts to distilled water prolonged 
the life of the plants which grew in it ; but that when magnesium instead 
of calcium salts were added they exerted a toxic influence upon the plants. 
The next work of importance upon the function of calcium appears to 
have been that of von Raumer and Kellermann (’80), which especially 
advanced the knowledge of the role of calcium in the transport of carbo- 
hydrates in the plant. Von Raumer (’83) carried their investigations still 
further and published them in a paper of fundamental importance. He 
seems first to have discovered the necessary ratio between calcium and 
magnesium. When plants were grown in distilled water, or in solutions 
lacking both calcium and magnesium, they made better growth than in solu- 
tions where only calcium was lacking. He showed that magnesium had a 
toxic action which could be counteracted by calcium. The plants ( Phaseolus 
