The remaining one (Lolium spp.) is one of the oldest 
domesticated pasture grasses. A brief description of the 
changes which occur in the Hordeae series follows: 
1. Agropyron Smithu Rydb. This species, which has 
a compact spike bearing multiflowered (6 to 10) spike- 
lets, is typical of the Hordeae. The bilateral plane of the 
rachilla is placed at a right angle to the bilateral plane 
of the rachis. Thus, both ranks of florets are apparent. 
The rachis is slender and continuous with no suggestion 
of either grooving or cupule development. 
2. Lolium subulatum Vis. Here the spikelets have 
turned edgewise and, in youth, become tightly com- 
pressed against the rachis (as is evidenced by a reduction 
of the inner (first) glume, except in the terminal spikelet 
where it is free to develop). The outer (second) glume 
elongates and conceals dorsally its spikelet against the 
rachis. 
3, 4. Aegilops (Triticum) cylindrica Host. and Tviti- 
cum monococcum L.. These species do not fit into the 
series perfectly in that their spikelets are placed as in 
Agropyron. They do, however, have pronounced cupu- 
loid cavities in the rachis-segments, especially in T'vvti- 
cum, where the cavity lining is pubescent and the lateral 
wings are conspicuous in having subtending notches. 
The rachis of Aegilops is continuous or tardily disartic- 
ulating. This character is recessive to the disarticulating 
rachis of its relative, wild emmer ( 7'r7t2ewm dicoccoides) 
and is thought to have been later transferred during the 
development of wheat spikes suitable for agricultural 
harvesting (Percival, 1926). The presence of a continu- 
ous rachis here, and in many of the other Hordeae, as 
well as in maize of the previous series, is basic in making 
these grasses of agricultural importance. 
5. Monerma cylindrica (Willd.) Coss and Dur. In 
this species solitary, uniflowered spikelets are embedded 
[ 284 | 
