DEVELOPMENT. "9 
gration of these elements has been well studied in the 
case of the wheat by M. Isidore Pierre, who has conclu- 
sively shown that what the leaves lose in these respects 
is gained by the ear. One important feature of matura- 
tion then consists in the gradual cessation of the work 
done in the leaf, the exhaustion of its supplies—carbo- 
naceous, nitrogenous, and mineral—and the transport of 
these materials to the organs of reserve, to the bark and 
young wood of the tree, to the seed in the case of wheat 
and other annuals, to the roots, bulbs, and tubers in 
other cases. In the case of an annual herbaceous plant 
like the wheat it appears that both root-action and leaf- 
action become reduced to a minimum, or are even 
altogether stopped some two or three weeks before the 
wheat is ready to cut, so that during that period no in- 
crease of weight of the plant as a whole takes place ; and 
if the ears themselves increase in weight, it is because 
they derive matter from other parts of the plant, which 
diminish in Weight in proportion. A few figures cited 
by M. Dehérain will illustrate the truth of these remarks 
—thus in the case of colza, out of a total of one thousand 
parts (grammes) of phosphoric acid in the entire plant, 
four hundred and fifty-six were found in the leaves in 
March, and only twenty-five in the leaves in June, while 
the flowering stems at the latter period contained eight 
hundred and sixty. Results of a similar character might 
be quoted in the case of potash and albuminoid matters. 
Tn all cases while the relative proportions gradually de- 
cline in the leaves they become correspondingly augment- 
ed in the flowering part of the stem and in the seeds. 
These results are attributed by M. Dehérain in great 
degree to varying degrees of evaporating power possessed 
by the leaves. According to him, the older leaves at the 
base of the stem evaporate but little as compared to the 
younger leaves near the top. These, by their superior 
evaporating power, cause the lower parts to be emptied 
