60 DROSERA ROTUNDIFOLIA. Cuar. TIL 
for a length equal to that of the glands. On the other 
hand, in the fresh leaf similarly treated, aggregation 
was plain in many of the tentacles after 15. m.; after 
65 m. it had extended down the pedicels for four, five, 
or more times the lengths of the glands; and after 
3 hrs. the cells of all the tentacles were affected for 
one-third or one-half of their entire lengths. Hence 
there can be no doubt that the exposure of leaves to 
carbonic acid either stops for a time the process of 
aggregation, or checks the transmission of the proper 
influence when the glands are subsequently excited 
by carbonate of ammonia; and this substance acts 
more promptly and energetically than any other. It 
is known that the protoplasm of plants exhibits its 
spontaneous movements only as long as it is in an 
oxygenated condition; and so it is with the white 
corpuscles of the blood, only as long as they receive 
oxygen from the red corpuscles ;* but the cases above 
given are somewhat different, as they relate to the 
delay in the generation or aggregation of the masses 
of protoplasm by the exclusion of oxygen. 
Summary and Concluding Remarks.—The process of 
aggregation is independent of the inflection of the 
tentacles and of increased secretion from the glands. 
It commences within the glands, whether these have 
been directly excited, or indirectly by a stimulus 
received from other glands. In both cases the pro- 
cess is transmitted from cell to cell down the whole 
_ length of the tentacles, being arrested for a short 
time at each transverse partition. With pale-coloured 
leaves the first change which is perceptible, but only 
* With respect to plants,Sachs, ‘Quarterly Journal of Micro 
‘Traité de Bot.” 3rd edit., 1874,  scopical Science, April 1874, p, 
v. 864. On blood corpuscles, see 185,’ 
