132 GERMINATION [CH. 
The plumule either pushes out from the same end of 
the caryopsis as the root (e.g. Wheat, Rye) or drives its 
way between the coats to the opposite end (e.g. Barley) 
and appears as a pointed cylinder of rolled leaves (the 
“ spear”) the outermost of which is sheath only, no lamina 
being developed. As Darwin showed, the pointed apex of 
such a plumule is hardened, facilitating the piercing of the 
soil above, and when the blade attains the open air it 
performs spiral movements during growth, indicating that 
similar attempts to rock from side to side have aided the 
plumule in forcing its way through the soil. It has also 
been shown that the apices of roots and plumules are 
sensitive to differences of temperature, of light-intensity, 
moisture and contact, all of which aid the seedling in 
establishing its position in the soil and in liberating the 
“spear.” For particulars the student should read Darwin’s 
Power of Movement in Plants. 
With regard to the established seedlings of grasses, 
many interesting details of structure are to be found in 
them. I have not sutfcient material to draw up a 
diagnostic arrangement of grass-seedlings, but it is 
evident that such could be done. It may be useful to 
illustrate this by the following tabular view of the 
characters of the larger seedlings of our common cereals, 
in part adapted from Vesque and Percival; though I find 
that some variations may occur, especially in the develop- 
ment of the auricles. 
