4.00 PROF. J. PERCIVAL ON THE OCCURRENCE OF 
nearer to the blade of the cotyledon than iu normal unmutilated 
plants of the same age. 
To study the effect of darkness upon the crystal-formation, 
seeds were germinated in the dark. Some were allowed to grow 
on the filter-paper, while others were placed in distilled water as 
before. In both cases the hypocotyls grew to a very great length, 
but the cotyledons were unable to free themselves from the testa 
of the seed. Crystals were not met with in any of these plants. 
Some plants grown in ordinary soil in the light until the 
cotyledons were free and the primary leaf just visible were 
covered with an opaque jar. The petioles of the primary leaves 
continued to grow, and the blades were pushed upwards for an 
inch or so, but remained folded. After 14 days the plants were 
examined and crystals were found in a similar position to those 
in plants grown in the same soil exposed to the light, the only 
difference noticeable being that the crystals in the petiole of the 
primary leaf of the darkened plants were much fewer than in 
normally grown specimens. 
Provided growth goes on, it would appear that darkness 
has but little or no direct influence upon the formation of 
calcium-oxalate crystals in these plants. It was observed that 
‘ plants grown in the dark in a complete culture solution, and also 
in the same solution in an atmosphere free from carbon-dioxide 
when exposed to light, the cotyledons are smaller and die more 
rapidly than those plants grown in distilled water under the same 
conditions. No doubt, if the salts of the culture-solution are 
absorbed by the plant and not utilized, they accumulate to 
poisonous extent and tend to damage the tissues of the leaves. 
A large number of seeds were germinated on filter-paper in 
Petri dishes in the usual way, and the seedlings were allowed to 
continue their growth in these. Where the plants were very 
crowded and the cover of the dish kept on, crystals did not form, 
although their primary leaves unfolded and grew almost as large 
as those of plants grown for the same length of time in exposed 
bottles and in which crystals were abundantly produced. 
A comparison was made between seedlings grown in the open 
and plants grown in the same box of soil, but covered with au 
inverted glass beaker to prevent transpiration. In the former 
erystals were more abundant than in the latter plants, their 
leaves were larger, and the vascular bundles were more completely 
developed. 
