MR. A. J. EWAET ON ASSIMILATORY INHIBITION. 379 
heating are the outer ventral leaves; the inner dorsal leaves, 
being shielded to a certain extent by the inrolling of the dried 
branches, resist longer. The leaves of Selaginella always contain 
a little air, hence the preparations must be kept in darkness 
when first made until the Bacteria cease to move, then exposed 
to light and examined. 
The Lichens are examined by means of thin sections, in which 
the assimilating activity of the gonidial cells can be determined 
without the Fungal respiration being able to exercise any 
disturbing influence. Bearing the greater delicacy and dis- 
criminating powers of the Bacterium method in mind, it is not 
surprising to find that by its help an assimilation and consequent 
evolution of oxygen can be detected in cases and under con- 
ditions in which, according to Jumelle, no such evolution of 
oxygen should have been perceptible. 
Thus Jumelle mentions that in plants of Cladonia rangiferina 
kept air-dried for three months and then moistened and 
examined, respiration was much weakened, and assimilation had 
almost entirely disappeared. Plants of Cladonia rangiferina 
and Evernia Prunastri, however, after being kept air-dried in 
wide open-mouthed bottles in darkness at 15° C. to 20° C., were 
for the most part living. On moistening, at first no perceptible 
or a mere trace of assimilation was shown, but after half an 
hour a moderately active, and after one hour a quite active 
evolution of oxygen is shown by the gonidia. 
As Jumelle does not state under what conditions his air- 
drying experiments were conducted, it is impossible to be certain 
whether or not other factors beyond the air-drying came into 
play in his experiments. Thus the temperature at which the 
air-dried plants are kept is a very important factor, and air-dried 
plants exposed to sunlight are much more rapidly injuriously 
affected than similar plants kept in darkness. 
In addition to this, the resistance which the plants offer to 
drying is largely dependent upon their vegetative vigour when 
collected. 
The plants of Cladonia experimented with in Table D were quite 
young and healthy, but the plants of Evernia were not nearly 
so vigorous. A few additional experiments made with some 
normally vigorous plants of Evernia, which were collected after 
the table had been completed, showed that with these more 
healthy and more resistant specimens an increased temperature 
LINN. JOURN.—BOTANY, VOL. XXXI. 2k 
