282 BOTANICAL GAZETTE [APRIL 
concentrated sulphuric acid, and increased oxygen pressure. 
Light may bring about some change in the coats of Rumex crispus 
to admit oxygen or other required substance, or permit the escape 
of some inhibiting substance such as an organic acid. It may 
change the relation of the lipoids from the oil water phase to the 
water oil phase, or break up a nearly continuous oil layer in the 
coat, thus allowing entrance or escape of some limiting factor. 
The presence of lipoids in the coats and the excretion of an acid 
instead of an alkaline substance during germination suggest that 
an enzyme acting in the coats hydrolyzes the lipoids, thus yielding 
acid and making the coats permeable to some required substance, 
or permitting the elimination of some inhibitory substance. 
There is some evidence of a coat effect in the germination of 
seeds of Oenothera biennis. While abrasion of the coats does not 
yield increased germination, hot water treatment and sulphuric 
acid treatment both yield considerable increases of germination in 
darkness. The presence of lipoids in the coats suggests the same 
explanation of the action of light as in the seeds of Rumex crispus, 
with the addition that the light may also have a beneficial effect 
on the constituents of the embryo. 
In the seeds of Nicotiana Tabacum, Verbascum Thapsus, and 
Daucus Carota there is little evidence of coat effects, there being 
no increased germination caused by abrasion, sulphuric acid 
treatment, hot water treatment, or increased oxygen pressure. . 
The only results suggesting coat effects are increased germination 
of Daucus Carota and Nicotiana Tabacum when soaked in hydrogen 
peroxide. This increased germination might be referred to the 
effects on the embryos. 
The seeds of this investigation fall into three groups. ~The first 
is represented by the seeds of Rumex crispus, in which the coats 
must be made permeable to some external or internal substance 
by light, abrasion, or other agency before abundant germination 
occurs. The second group is represented by the seeds of Oenothera 
biennis, whose germination is partly dependent on the coats being 
made permeable, and partly on the activation of the embryos by 
light or chemical agencies. The third group is represented by seeds 
of Nicotiana Tabacum, Daucus Carota, and Verbascum Thapsus, 
