22 
to the sand without vegetable growth soon gave evidence of putre- 
faction. On the other hand, no signs of putrefaction showed 
themselves in the pans in which the rye grass was growing. It thus 
appears that the fibrille of rye grass assimilate nitrogenous matter, 
without that matter first undergoing decomposition into its ultimate 
elements, unless it be contended that decomposition is set up by 
contact with the fibrille of the rootlet itself. If this argument is 
used, then I contend that even in that case the nitrogenous com- 
pounds are seized upon in a nascent state, and do not lose their 
vitality by the process. This vitality would be entirely lost if 
actual decomposition did take place, and chemical matter was 
formed. It is this action which makes the difference between car- 
nivorous plants and graminivorous or chemical salt feeders. The 
ordinary run of plants require the decomposition of vegetable matter 
into certain elements, such as ulmic, humic, geic, aprocenic, and 
crenic acids, before they can assimilate it in a proper manner. It 
is in this very decomposition that we have one of the most won- 
derful provisions of nature. It is the presence of these acids which 
enables garden mould to deodorize decomposing excretia so effec- 
tually, in a way that nothing else in nature will do. It is this class 
of acids which result from vegetable decay which enables soils to 
retain animal débris, and present it ready for the formation of plant 
life ; and nothing has ever been discovered which will remove the 
ammonia from sewage except earth acids and carnivorous 
plants. The latter will remove matters which manufacture 
ammonia without the intervention of earth acids; for rye grass 
will grow in silver sand if fed with beef tea or ordinary dish 
washings; but vegetable feeders will not do so. For them time 
is requisite for the decomposition of animal matter into its 
original elements, and the stage which has been called previous 
sewage decomposition must be reached before plant growth will 
take place. It has been supposed by eminent physiologists that 
carbonic acid is mainly absorbed by the leaves of plants from the 
atmosphere, and decomposed by the agency of light, oxygen being 
given out in the process. ‘This is true in regard to a large part of 
the vegetable kingdom, but it is not so at all times. It does not 
follow that it is absolutely necessary for carbon to be absorbed as 
carbonic acid; take the instance of a seedling potato grown under 
glass in a way by means of which the access of carbonic acid shall 
be denied. It will grow and produce green haulms, assimilating 
and forming woody fibre out of the potato, without the material in 
the potato undergoing previous decomposition, and being resolved 
into its elements. Carnivorous plants are able to assimilate food in 
a similar manner; they seize upon the living matter which exists in 
sewage, and build up their structures from it, sending out oxygen 
into the atmosphere, but, like fungi, producing carbonic acid at 
their extremities in the soil or water. Dr. W. B. Carpenter says 
