Embryo and Aleurone Layer of Hordenm. 815 
The following experiment throws some light on the question as to 
whether mineral salts or certain of them stimulate the elaboration and 
excretion of amylase by the embryo ; that is to say, whether their influence 
is to be regarded as physiological or otherwise. 
We have seen that the secretory activity of the embryo cultivated upon 
a 0-55 % solution of asparagin is minimal. 
If we take such culture solutions upon which embryos have been 
growing for some days and digest them separately with (1) soluble starch 
alone, or with (2) soluble starch containing mineral salts in the concentrations 
in which they occur initially in the small quantity (10 c.c.) of culture medium 
employed for each plate culture, the results should indicate whether the 
influence of these salts takes place externally, i. e. merely protects the 
amylase secreted during the culture period, or whether they influence the 
general metabolism of the plant and, consequently, its secretory activity. 
The following experimental results, taken in conjunction with those of 
Tables I and II, favour the latter alternative, namely, that the influence 
they exercise is mainly physiological. 1 
TABLE III. 
Digestions of Culture Medium with Soluble Starch in the 
Presence and Absence of Mineral Salts. 
Digestion period. 
1. 20 hours 
Composition of 
digestion mixture. 
Starch only 
Starch and 
mineral salts 
Amylase per 20 objects 
in culture medium 
{equivalent to mg. of Cu). 
6-o 
4.0 
The culture liquids investigated were derived from two cultures of 40 
embryos each, cultivated on 0-055 % asparagin for seven days. 
It is obvious from the above results, by comparison with Experiment 3, 
Table I, that the mineral salts used in the experiments previously described 
enter in some way into the general metabolism of the embryo, and thereby 
influence its secretory functions, thus negativing the suggestion that under the 
conditions of culture employed they—or certain of them, notably the phos¬ 
phate—function as protective agents to the enzyme excreted into culture 
medium. It is not denied that they do not function in the manner indicated 
during certain phases of the culture experiment, but it is suggested that 
they principally influence secretion by entering into or influencing the 
general metabolic activities of the plantlet. 
In order to demonstrate further the possession of an amylo-secretory 
function by the embryo, cultures of these objects were established on 
a medium consisting of 5 % gelatine and finely ground barley endosperm 
1 H. M. Richards : Ann. Bot., xxi, 1907, p. 501, 
3H 2 
