SMITH: THE HISTOLOGY OF CERTAIN ORCHIDS 5 
Schilling’s view (1894) as to the function of slime cells in 
water plants was that they are water regulators for the young parts 
without a protective epidermis, which disappear as soon as the 
outer tissue has developed. 
Kohl (1899) has given an extensive account of raphides and 
their relations to plant slimes. In summary he finds that they 
consist of calcium oxalate; that they belong to the monoclinic 
system (though they are in many cases impossible for a crystallo- 
grapher to define because of the smallness of the needles, their 
large angles and the curvature of the crystal face); that they 
appear very early in the development of the organ in which 
they occur, having been observed one millimeter from the 
growing point; that the number of cells containing them increases 
with the unfolding of the plant part; and that as soon as the 
cell bearing them has reached its typical form it remains re- 
latively unchanged during its whole subsequent existence. 
Kohl notes that in the course of his observations he has never 
found that the raphides disappear. He describes their develop- 
ment as follows: they originate in vacuoles singly or in numbers, 
each crystal being ensheathed in a plasma membrane, and the 
mature bundles being bound together in a cytoplasmic sheath 
attached to the primordial utricle by cytoplasmic strands. 
The nucleus in the mature cell is commonly pushed to one 
side while the crystals occupy the center of the cell, which 
enlarges during the development of the raphides and usually in 
a longitudinal direction. In some forms cells bearing raphides 
have been observed which are twenty times longer than wide 
(Vanilla planifolia). Sometimes when these cells occur in series, 
the cross walls between them may disappear entirely, due to 
their vigorous growth in length. According to Kohl the crystals 
remain unchanged in size and number until the cell disintegrates. 
Sooner or later these cells contain a homogeneous translucent 
slime. He Says, e ‘Dieser Schleim ist bai jedenfalls, welche die den 
Raph hiden g veranlasst. ” Kohl 
gives a list of plants which contain cells bearing raphides. This 
list comprises over one hundred species of monocotyledons and 
thirty-four species of dicotyledons. 
Mobius (1908) attributed to mucilage in cells bearing 
raphides the réle of protecting the protoplasm from injury by 
the pointed crystals. 
