138 CYCLOSIS. 



currents are directed from right to left, or the reverse, accord- 

 ing to no apparent rule. Tiie contiguous rows of vessels anas- 

 tomose from place to place, which produces a permanent inter- 

 ruption of the risinpr and falling currents. Iti order to ena- 

 ble the circulating motion to take place, it is necessary that 

 the system of vessels should be reticulated. It often happens, 

 that when strong currents are formed, weak ones disappf^ar. 

 In cases when the cyclosis cannot be actually seen in the ves- 

 sels, it m;\y be inferred from the following fact. When the 

 two ends of a stem containing njilk are cut through, the latex 

 is seen to run out at both ends of the fragment, which proves 

 that there must be both an ascending and descending current ; 

 the same phenomenon is visible in plants, having a colorless 

 latex, therefore there must be a motion of ascent and descent 

 in them also. 



1^6, "Cyclosis occurs in the greater part of monocotyle- 

 donous, and dicotyledonous plants, and the vessels in which it 

 takes place, are so generally in connexion with spiral vessels, 

 that the presence or absence of the one is usually accompanied 

 by that of the other. The situation of the vessels in which 

 it is found is in the root, stem, petiole, peduncle, flower, &c." 

 187. The latex is a highly elaborated, and highly organized 

 juice. It is usually viscid, insoluble in water, often opaque, 

 colored white, yellow, brown, red, and is also transparent and 

 colorh'ss, differences that result from the nature of the organ- 

 ized globules it contains, which, according to Mr. Schultz, 

 constitute the living part of the latex. These globules have 

 an oscillating motion, and like the globules of the blood, they 

 coagulate and the liquid part becomes transparent. Upon 

 exposure to the air, the latex separates into a coagulum of a 

 tenaceous elastic qualil)^ and a serum ; the former being some- 

 what analogous to caoutchouc. This property is not found in 

 any other vegetable secretion. If we consider the organiza- 

 tion of the latex, the globules it contains, its property of co- 

 agulation, and separating into serum and a sort of fibrin, we 

 are tempted to believe that there exist a considerable analogy 

 between it and the blood of animals. 



188. The latex itself originates in the sap, which rises by 

 the tissue of the wood, and introduces itself into the foliaceous 

 organs, thence after being elaborated, passing into the bark 

 where it is deposited in the vessels in its mature form. The 

 function of the latex is to nourish the tissue amons: which it 

 is found. The loss of only a small quantity of latex, injures a 

 plant very much. It is the phenomenon of autosyncrisis and 

 autodiacrysisj (attraction and repulson of the globules) which 



