ECOLOGY 139 
former. Emmer differs from wheat in that the whole spikelet con- 
taining several seeds becomes a fruit and breaks away from the 
rachis entire. The seed-like fruit of foxtail millet (Chetochloa italica) 
and proso millet (Panicum miliaceum) consists of a coriaceous lemma 
and palea tightly inclosing the thin-walled caryopsis. In all these 
cases the root breaks through the back of the lemma near the base 
by splitting the tissue and the shoot pushes up through the space 
between the caryopsis and the lemma, emerging near the tip. In 
Johnson-grass (Holcus halepensis) the grain is enveloped by the 
hard glumes and delicate lemma, sterile lemma and palea. The 
tissue of the glume appears to be too firm to permit the root to 
penetrate, for it passes through between the glumes. The fruit of 
tall oat-grass (Arrhenatherum elatius) consists of 2 florets, only the 
second of which is fertile. The root passes through the back of the 
lemma of this floret. Rice germinates in a manner different from 
that of the other fruits described. The caryopsis is inclosed in the 
much-flattened and keeled lemma and palea. The shoot breaks 
through the back of the lemma at the base and appears first as a 
pointed organ at the base of which later emerge the roots. 
175. Propagation by bulblets.——Some grasses of high 
latitudes and altitudes produce, in the inflorescence, 
bulblets in place of ordinary spikelets. Bulblets are 
spikelets or portions of spikelets, in which the floral 
bracts have been transformed into small leaves, the whole 
becoming a vegetative shoot. These bulblets, which may 
be provided with young roots, fall off and produce new 
plants. A number of species may, under certain con- 
ditions, produce bulblets, while a few do this uniformly in 
certain regions (Poa bulbosa L.). Certain species (as Poa 
alpina L.) are ordinarily sexual but in extremes of alti- 
tudes and latitudes are asexual. 
PLANT SOCIETIES 
176. So far as concerns their adaptation to environ- 
ment based upon condition of moisture, grasses may be 
