185 
protected to retain its vitality, in the extremes of our climate. It 
would appear that the seed is not in surroundings congenial to 
its nature, and has not yet been able to adapt itself to its en- 
vironment. This also doubtless explains the paucity of species 
found in the Northern United States. The seeds are beautiful 
objects under the microscope. Elegant in outline their beauty is 
enhanced by the graceful curves of the cell-margins, which often 
wind into fantastic figures, or build up the testa with cells of 
mathematical exactness. The clearness of the cell wall in some 
species (Listera cordata) reminds one of the valves of a diatom, 
while a study of the delicate markings on the inner surface of the 
cell, tax not a little the patience and skill of the microscopist. 
I have been greatly interested in the examination of specimens 
of the so-called Vanilla Bean, gathered in various parts of the 
world. The value of these pods varies greatly, dependent upon 
the locality in which they grow. So close is their resemblance, 
however, that the merchants have great difficulty in distinguish- 
ing them. The testa is very thick and strong. Instead of a 
ribbed surface the whole outer wall, save a slit-like central portion, 
is evenly thickened and forms a heavy plate. Save in this partic- 
ular and their dark reddish brown color, the seeds are identical in 
structure with those of our native orchids. The resemblance of the 
eight specimens examined is very close. With perhaps two excep- 
tions, the seeds would appear to belong to the same species. In 
the other specimens some variations were noticeable, probably due 
to climate. The constancy of these features as a basis of distin- 
guishing them would necessitate a wider comparison than I have 
been able to make. 
In examining the seeds of our Eastern orchids examples were 
chosen in each case that as far as possible would be typical of the 
species. The estimates are made upon normally developed seeds, 
which were not distorted by luxuriant growth or dwarfed by un- 
toward circumstances. I believe that a wider study of the forms 
will make no material change in the data presented. In all pos- 
sible cases comparison of fruit from widely separate localities has 
been made, and with rare occurrence has marked variation of the 
seed been manifest. Occasionally the sculpturing of the cell-wall 
changes, and often the variation of the cell dimensions is consid- 
