Hie Seed and its Gemination. 
505 
lupin from a further decomposition of the peptone under the 
influence of the same ferment. It can be traced about the young 
plant, and can be shown to travel along its tissues up towards 
the seats of active growth. 
The appearance of this crystalline body at the expense of 
proteid is not a phenomenon peculiar to vegetable life. Precisely 
similar decompositions are brought about in the intestines of 
animals. In the stomach a great part of the proteid matter of 
the food is converted into peptone and absorbed into the blood ; 
part, however, goes on into the intestine, where the secretion of 
the pancreas or sweetbread meets it. This contains a ferment 
which brings about changes which resemble those of the lupin 
seed, the proteid being converted first into peptone and then 
into crystalline bodies called leucin and tyrosin. These are 
both nitrogen-containing bodies and correspond to the asparagin 
of the plant. They all belong to a group known to chemists 
as " amides." 
The ferment in pancreatic juice which brings about this 
transformation is known as trypsin, and that of the lupin seed 
may therefore be called vegetable trypsin. 
There is a peculiarity about the ferments which digest 
proteids that is less noticeable in the case of those which affect 
carbohydrates, which is that they require some other medium 
than a neutral one for their activity to be manifested. The 
vegetable trypsin works most energetically in a faintly acid one, 
and cannot change the proteids at all if the fluid be alkaline. 
Observation of the seed during germination shows that its sap 
is neutral at first and soon changes to a faintly acid reaction. 
A very marked difference between the barley and the lupin 
appears with regard to the distribution of the ferment in the 
seed. In the former, this has been shown to be confined to the 
scutellum, and to a particular layer of cells in this. In the 
lupin, on the other hand, there is no such limitation. The fer- 
ment is distributed throughout the substance of the cotyledons, 
wherever the reserve proteids are stored. The difference in dis- 
tribution involves a difference of procedure. In the barley the 
ferment is formed continuously in the epithelium of the scu- 
tellum, and thence is poured out, or extruded in some way, into 
the endosperm. In the lupin it is formed once for all in each 
cell where the reserve materials are accumulated. 
The germination of the seed of the castor-oil plant (figs. 4, 5) 
throws light on the general question of the fate of the oil or fat 
which is found in variable quantity in so many seeds. As said 
above, the quantity present in the castor-oil seed may amount to 
nearly GO per cent, of its dry weight. It is on account of its 
VOL. I. T. S— 3 L L 
