ON THE FLUIDS OF PLANTS. 
401 
Creeper; there are a great many Robins'^ about. Returning from Hudson 
to-day, I saw two large round-winged Hawks, as big as Buzzards, and having 
the same cry ; they were soaring very high, and in circles. I also saw another 
male Baltimore ; these and the Blue-birds appear much brighter living than dead. 
I go on to Utica to-morrow, for a few days. 
Hudson^ May 7, 1837. 
ON THE VITAL MOTIONS OF THE FLUIDS OF PLANTS. 
By Edwin Lankester, M.R.C.S. 
As the question of the cause of the absorption and progression of sap in plants 
has lately occupied the attention of some of your correspondents, perhaps you will 
allow me to make a few remarks on the same subject. The cause of the motions of 
the sap has long beeen a vexata questio amongst botanists, and many and varied 
have been the theories attempting to account for it. Much of the perplexity 
attendant on this subject arises from our ignorance of the minute structure and 
intimate nature of those parts of the plant that convey the fluids to the 
different parts of its system; and therefore, perhaps, in the present state of our 
knowledge on these points We must expect that every theory offering an ex¬ 
planation of these phenomena will be more or less chimerical. In considering 
this subject, also, it is much easier to demolish a theory than to substitute a 
better in its place. However, as the subject is one on which at present few 
botanists entertain the same opinion, the following observations may not be 
altogether uninteresting. 
Many of the speculations with regard to the ascent of the sap have depended 
on the ideas entertained by the botanist on the nature of the vegetable tissues 
in which this takes place. Some have supposed that the sap ascended in straight 
uninterrupted tubes, and this was one reason for concluding that the sap ascended 
as in capillary tubes. There is, however, no proof of the existence of such 
tubes, or that the sap ascends in a continuous vertical direction at all. The 
principal forms of vegetable tissue in which sap ascends are ducts (which appear 
to conduct either air or sap, according to circumstances), vasiform tissue, cellular 
tissue, and woody fibre. None of these forms of tissue are tubes continued 
from one end of the plant to the other; it is, therefore, impossible that the sap 
should be affected in the same manner as fluids in continued tubes. 
Four distinct kinds of motion have been observed to take place in these 
tissues. First, the general ascent of the sap, which is constantly going on to a 
* We presume Tiirdus migratorltis is the species here alluded to bj Mr. Doubleday_ En . 
