1921] GARDNER—GERMINATION 333 
Mechanical rupture 
In 1906 CRockER (7) succeeded in germinating a number of 
different kinds of seeds after breaking the seed coats. KInzeL (24) 
found that puncturing coats of some of his light sensitive seeds 
gave better germination in darkness. GassNER (13) found that 
rupture of the coats of seeds of Chloris ciliata permitted good 
germination in darkness at 34°C. Thus it seemed quite possible 
that the seeds under investigation might be brought to germination 
by such treatment. Accordingly a more carefully controlled 
experiment was made to determine the réle of the several seed 
Coats in germination. Seeds of each kind were rubbed on fine 
sandpaper and placed on moist filter paper in Petri dishes. The 
Petri dishes were carefully wrapped in black cloth and placed in 
a dark room at 24-30°C. for 8 days. Concurrently, sets of 
unabraded seeds were placed to germinate in light and darkness. 
TABLE IV 
Not 
Not ABRADED ABRADED | ,noapep 
SEEDs 
Light Darkness | Darkness | Darkness 
Nicotiana Tabecits..,..0.05.,.-5.31 60, 61 0, oO o, I o, 1 
Mines C0 sg. 30, 16 0, I 40, 66* Q, 
Verbascum AE ee a 75,32 o, 8 fa 1, 3 
there hehe re, 10, 39 ,o a, 5 7, 1 
Danes Carol ee 1 7 25,15 21,17 
* Coats off. 
Mechanical abrasion of seed coats for various periods in rotating 
cylinders containing coarse quartz sand gave similar results. 
examination of the data in table IV reveals the beneficial effect of 
abrasion of seed coats in but one instance. In the case of Rumex 
crispus abrasion of the seed coats yielded a percentage of germina- 
tion slightly exceeding that for light in the control, while the removal 
of the coats yields a percentage of germination even more than 
double that in light. This suggests that the seed coats of Rumex 
crispus inhibit or retard the entrance of some necessary factor, 
or perhaps retard the exit of some inhibiting factor, and that light 
in some way favors these movements. 
