of Cosson are distributed between the Biformes and Con- 
Jormes. Unfortunately several wild species are not con- 
sidered. The disposition of species by Thellung is: 
Subsect. I. Byformes 
A, sterilis ssp. 1 macrocarpa 
ssp. 2 byzantina 
Subsect. II. Conformes 
A. fatua ssp. 1 fatua 
ssp. 2 sativa (incl. A. orientalis) 
ssp. 3 nuda 
A. strigosa ssp. 1 barbata 
ssp. 2 strigosa (incl. A. brevis) 
ssp. 3 Wiestit 
ssp. 4 abyssinica 
The system of Mal’tsev was developed after an exten- 
sive study of herbarium material and of a series of plant- 
ings of Avena species in various parts of the U.S.S.R. 
The material was gathered by the expeditions of Vavilov 
and associates, the geographical and ecological data col- 
lected by the expeditions being used in the treatment. 
On the basis of chromosome numbers Mal’tsev divided 
the section into subsection Aristulatae and subsection 
Denticulatae. Subsection A ristu/atae contains the diploid 
and tetraploid species. It is regarded as the older, per- 
haps derived from section Avenastrum, with its center 
of origin in the western part of the Mediterranean region. 
Subsection Denticulatae contains the hexaploid oats and 
is believed to be the younger. It is regarded as having 
arisen from an unknown ancestral complex in the moun- 
tains of Central Asia, a conclusion which Schiemann 
(1982) says has not been shown to be based on fact. The 
characters used by Mal’tsev to define his subsections and 
series will be given in the key. In the following outline 
of the system all cultivated oats are marked by asterisks 
and each is believed to be derived from the wild subspe- 
cies which immediately precedes it. The division into 
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