396 PROF. J. PERCIVAL ON THE OCCURRENCE OF 
The Occurrence of Calcium-oxalate Crystals in Seedlings of 
Alsike (Trifolium hybridum, Linn.). By Prof. Joan 
PercivaL, M.A., F.L.S. 
[Read 5th June, 1902.] 
Tue very definite and characteristic position in which the crystals 
of calcium oxalate occur in the leaves of most leguminous plants 
led me to consider that a detailed study of their first appearance 
and distribution in young seedlings would be of interest, and 
might possibly throw some light upon their formation. 
The seedlings were grown under the different conditions 
described below, and after reaching various stages of development 
were placed first in boiling water, then in alcohol, and finally 
transferred to chloral-hydrate on large glass slides, where the 
complete plants could be examined. Polarized light was generally 
employed to determine the presence of the smallest crystals. 
Various species of Leguminose were tried at first, but Alsike 
was eventually selected for further examination on account of 
the absence of hairs upon the surface of the plant, which facili- 
tated the examination of the internal tissues of the cleared 
specimens, 
The seeds were germinated upon the purest filter-paper 
moistened with distilled water. 
Germination occurs in a few hours, and the cotyledons become 
free from the testa and develop a green colour in three or four days. 
At this stage of growth no crystals are present anywhere in the 
plants. As soon as the plants were sufficiently large to handle, 
they were removed from the filter-paper bed, and placed with their 
roots dipping into small bottles of distilled water, the bottle being 
lined with paraffin to prevent contact of the water with the 
glass. The water used was distilled in a metal still and collected 
in paraffin-lined flasks. Rapid growth takes place as soon a8 the 
plants are allowed a free supply of water, and by the time they 
are six or eight days old the small folded primary leaf can be 
seen between the bases of the cotyledons. 
At this stage of development, crystals appear along the 
vascular bundles in the petioles of the cotyledons, and are dis- 
tributed evenly from a point close to the blade down to the con- 
nection of the bundle with its continuation in the hypocotyl of 
the seedling. Above and below these limits, crystals very rarely 
develop at this or any subsequent stage of growth. 
