2 jo Kny. — On Correlation in the 
been removed by means either of a pointed scalpel or of 
a specially adapted pair of scissors. In those of the third 
series were placed seedlings in which the roots had been 
removed, the plumule being left. In other respects the seed- 
lings in the three series were quite similar. It was, however, 
found necessary, in the case of Vicia Faba , to remove one of 
the cotyledons in the seedlings of all three series ; for other- 
wise it would have been impossible to remove the plumule 
with a clean cut. Previously to the commencement of the 
experiments, the seeds to be used were kept for some time, 
until the protrusion of the radicle, in shallow dishes either 
with water ( Vicia Fab a) or on very pure wet sand, and were 
carefully selected so that the seedlings of all three series might 
be equally vigorous and equally developed in the same time. 
The germinating seeds were so placed on the glass dish or 
earthenware plate under the bell-jar, that the tap-root ( Vicia 
Faba ) or the most vigorous root (Zea Mays) could only grow 
over the edge into the moist air. 
In the more rapidly growing Zea Mays, the seedlings were 
inspected every day ; in Vicia Faba they were inspected 
every day or every two days as circumstances required. In 
order to neutralize the injurious effect of a short exposure 
to dry air, the seedlings on inspection were at once placed, 
after the removal of the bell-jar, in a dish of water, and 
then, in the case of the seedlings of Series 2 and 3, any newly 
formed adventitious shoots in the former, and any newly 
formed adventitious roots in the latter, were carefully re- 
moved. In order to maintain, as far as possible, uniformity 
of conditions, the seedlings of Series 1 were also placed, at 
each inspection, for a time in a dish of water. In all cases 
the water was, as far as possible, shaken off the seedlings 
before they were replaced under their respective bell-jars. 
Each experiment was terminated when the roots had 
nearly reached the water in the saucer under the bell-jar. 
By this time the shoots had grown so that they had almost 
or quite reached the curved roof of the bell-jar. 
The method of weighing was adopted for the purpose of 
