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 Turdtu migratoritts is the species here alluded to by Mr. Doubleday Ed. 



