1910] Pease & Moore,— Agropyron caninum and Allies 61 
Europe. Its great scarcity makes me wonder more and more at my 
Shelburne experience. What was the peculiar local influence which 
‘aused fertility at this station and time? Was it a matter of soil-con- 
ditions, weather, insect visitors, or the purely casual reappearance of 
an ancestral trait? To these questions there is no answer as yet 
apparent. I shall be interested to learn whether the plants fruit again 
as abundantly, if at all, this coming season. I sincerely hope that the 
search of those enthusiasts above mentioned will be rewarded as mine 
was. 
CAMBRIDGE, MASSACHUSETTS. 
AGROPYRON CANINUM AND ITS NORTH AMERICAN 
ALLIES. 
ARTHUR STANLEY PEASE and ALBERT HaNronp Moore. 
THE genus Agropyron is, as is well known, a very puzzling one. 
Two recent revisions ? have, in the opinion of the writers, not entirely 
cleared up the difficulties presented by the relatives of Agropyron 
caninum (L.) Beauv. The difficulty of indicating the rank and rela- 
tionship of the members of the group by a series of independent species, 
as has generally been attempted, arises from an extraordinary amount 
of intergradation. Agropyron caninum passes, by the loss of its awns, 
to A. tenerum Vasey; the latter to A. violaceum (Hornem.) Lange, by 
the shortening and often thickening of the spikes; this again, on the 
one hand to A. violaceum (Hornem.) Lange var. latiglume Scribn. & 
Sm., by the flattening out of the keel and the presence of pubescence on 
the spikelets, or to A. violaceum (Hornem.) Lange var. andinum 
Scribn. & Sm., by the presence of awns. Forms in which the awns 
are strongly bent outward have been described as Triticum caninum 
L. var. Gmelini Ledeb., which may also be regarded as Triticum 
1 The authors desire to express their thanks to the staff of the Gray Herbarium for 
the privileges and valuable suggestions received from them. 
2F, Lamson Scribner and J. G. Smith, Native and Introduced Species of the Genera 
Hordeum and Agropyron. Studies of American Grasses, U. S. Dept. Agr. Div. Agrost. 
Bull. no. 4, 25-23 (Feb. 6, 1897); C. V. Piper, Agropyron tenerum and its Allies, Bull. 
Torr. Bot. Club, xxxii, 542-547 (Oct. 21, 1905). 
