A Classification of the Varieties of Cultivated Oats 97 
ferred to the Department of Farm Crops and came to the hands of the 
writer, by whom, in cooperation with the Office of Cereal Investigations, 
the work of classification was continued. During the years 1913, 1914, 
and 1915, the original collection has been supplemented by accessions 
from the Office of Cereal Investigations and from various other sources, 
all of which have supplied many new varieties or old varieties under 
new names that have appeared in the catalogs of seedsmen or in the 
reports of experiment stations. 
During the time that the collection has been in the hands of the writer, 
the varieties have each year been grown in rows one rod in length spaced 
one foot apart. The plants were thinned to spaces of six inches in the 
row, thus giving equally to each plant a sufficient area in which to develop 
its growth. 
MORPHOLOGY OF THE OATS PLANT 
The following discussions present in considerable detail the morphology 
of the oats plant. The important taxonomic characters are described and 
their uses in previous classifications and in the present one are explained. 
THE CARYOPSIS 
In the characteristic spikelet of Avena the lemma and the palea firmly 
clasp the caryopsis, and the three parts combine to form the oats grain. 
The caryopsis, or kernel, presents in itself no morphological differences 
that may be utilized in classification; for it is always more or less spindle- 
shaped, furrowed on one side, and hairy at the tip and on the sides. The 
close investment of the kernel by the lemma and the palea, however, is 
an important character and serves to distinguish all other species of 
Avena from Avena nuda, in which the caryopsis is loose and free within 
its bracts, the parts readily separating. This characteristic of the 
A. nuda spikelet is considered by all systematists a specific distinction, 
and it presents the only case in which the caryopsis is directly concerned 
in the classification of varieties of oats. 
BASILAR CONNECTION OF THE GRAINS 
Among certain wild types of Avena the peduncle of the spikelet is 
slightly inserted into the callus of the first grain, and the junction of the 
two parts forms a well-articulated joint at which they easily separate 
when mature. The articulation of the second and third grains, however, 
