LIFE HISTORY OF TIMOTHY 37 
tending outward from the axis, and forming a dense cylindrical 
inflorescence (13, p. 10-11). 
At the base of each spikelet are the two glumes. The pistil and 
stamens of the single floret of each spikelet are inclosed in the lemma 
and palea. The two glumes, the lemma, and the palea are arranged 
alternately, like the leaves of a shoot, in two ranks (4, p. 17-20). 
The appearance of a timothy spikelet, with a floret in bloom, is illus- 
trated in Plate 7, G. 
The palea of the floret and the prophyllum of branch shoots in 
grasses are commonly regarded as homologous. This theory is 
based upon the facts that one stands between the rachilla and a 
floral branch, the other between the stem and a vegetative branch 
(17, p. 118, 127) ; the relative positions of the palea and of the 
prophyllum are the same, each having its back to the axis on which 
the branch is borne (If, p. 17) ; in grasses both the palea and the 
prophyllum are usually 2-nerved or 2-keeled, instead of having a 
single prominent midrib, like the leaves (Ifi, p. 59). 
On plants of some species of grasses having florets borne singly 
in the spikelets the florets are apparently terminal on the rachilla, 
instead of growing laterally as on plants of species having several 
florets to each spikelet (17 p. 132). In Plate 8, D and E, each 
floret or modified floret is growing at the tip of the abnormally 
elongated axis, which, it is assumed, represents the rachilla. Al- 
though the axes of these spikelets do not extend beyond the bases 
of the florets, the axis of each floret is at a slight angle to the rachilla, 
which indicates that in timothy the floret is not terminal. 
The inflorescence of timothy has been fully described in various 
textbooks and other botanical publications (13 p. 10-11; 29, p. 123; 
18,p.U0-Ul). 
GROWTH OF THE HEAD 
A timothy head emerges from the upper leaf sheaths of the culm 
when the shoot has attained about one-half of its final growth in 
length. A rudimentary head, however, can be found if the inclos- 
ing leaf sheaths are removed on a large and vigorous shoot several 
weeks earlier. 
Timothy shoots were collected from an ordinary meadow at inter- 
vals of one week from May 1 to July 3, 1916. Five shoots, each 
with a head or with the rudimentary part from which it develops, 
were examined on May 1 ; on each later date when observations were 
made 10 shoots were examined. The average length (in inches) of 
timothy heads on different dates in 1916 was as follows: May 1, 
0.09; May 8, 0.10; May 15, 0.12; May 22, 0.22; May 29, 0.59; June 
5, 1.86; June 12, 2.83; June 19, 3.52; June 26, 3.76; July 3, 3.70. 
The heads made their most rapid growth in length from about 
June 1 to 20. The culms, which also made a relatively rapid growth 
in length during the same period, continued to grow for about three 
weeks after the heads had ceased to increase in length. 
In another series of measurements, made in 1916, of 14 timothy 
shoots, the average date on which the heads had completely emerged 
from the upper leaf sheaths was June 19, when the shoots had grown 
to 53.9 per cent of their final length. 
At the time when these 14 heads had just emerged from within 
the inclosing leaf sheaths their average length was 3,9 inches. On 
