CYCL0SI8. 125 



that it does not flow in the summer, viz., vital action commences 

 in the buds, and the sap is directed to them ; but when it freezes 

 again at niglit, the sap will flow the next day, as the vitality of 

 the buds is checked or suspended in its action by the cold. 



Section 6. — Ci/closis. 



230. In the cinenchyraa there has been discovered a circula- 

 tion called cyclosis ; the term, we presume, is derived from 

 kuklos, a circle. The cinenchyma, as we have before described 

 it, has its arrangements in no regular order, but lies imbedded 

 in the other tissues, running in every direction. In this tissue 

 the cyclosis takes place; the circulating fluid being generally, 

 though not always, a milky substance, and is called latex. The 

 latex, which conveys granular matter, circulates through a plexus 

 of reticulated vessels in all directions ; when the vessels are 

 parallel, and near each other, the currents rise in some and fall 

 in others ; but, in connecting or lateral vessels, the currents are 

 directed from right to left, or the reverse, according to no ap- 

 parent rule. The contiguous rows of vessels anastomose from 

 place to place, which produces a permanent interruption of the 

 rising and falling currents. In order to enable the circulating- 

 motion to take place, it is necessary that the system of vessels 

 should be reticulated. It often happens, that when strong cur- 

 rents are formed, weak ones disappear. In cases when the 

 cyclosis cannot be actually seen in the vessels, it may be inferred 

 from the following fact : When the two ends of a stem contain- 

 ing milk 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 a 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. 



231. In the cells of some, at least, of the lower orders of 

 plants, there is a circulation in the individual cells called the 

 circulation of rotation^ which has excited much interest. The 

 Chara fragilis has long been a subject of notice. As early as 

 1774, Corti, an Italian physician of Lucca, discovered the circu- 

 lation in the tube of the Chara. 



The Chara is an aquatic plant, consisting of slender stems 

 with a central tube surrounded by numerous small cortical 

 tubes, all of which are filled with a fluid having minute globules 



230. What is cyclosis ? What is the fluid called ? How do the currcjits 

 move? — 231. When does the circulation of rotation take place? What 

 plant has been long noticed ? Who discovered the circulation ? Describe 

 the Chara. 



