CYCLOSIS. 137 



we resort to cxosmose it can only pass out into the ascending 

 current, an«l l>v l)econiing lighter by dilution, is drawn by En- 

 do — •> ill! ncdiately back again. But our author solves the 

 d. \", by saving that f^ravity will carry the denser sap 



downwards ! True, but how comes ihe denser sap separated 

 from the ligliter ? and wiiy docs it not return in the same 

 vessels in which it ascends ? 



1S4. How does gravity operate in carrying the denser 

 fluid upwards, as in many cases in which the extremities of 

 branches are lower than the point of insertion ? We know of 

 no solution to these qicstions, and we are compelled to say 

 that they are ficts ot' which we can only refer to the action 

 of that mysterious principle which we call life. The action 

 of this principle, is of course, moditied by circumstances. It 

 requires the action of external agents to call it into operation, 

 and its tbrce is increased t)r retarded by the same. Heat and 

 moisture exercise great influence over it in circulation. In 

 the cold of winter it is nearly : uspended. but the warmth of 

 spring calls it into action. After its action has commenced 

 with som? vigor, a cold night seems to retard or sMspend its 

 operations for the succeed. ng day. Tliis is seen in the Sugar- 

 Maple. The sap commences to flow from the incisions, when 

 the warm d lys and cold nights of spring come on. But if 

 several successive nights, are so warm that it does not freeze, 

 the sap ceases to fljw, and lor the same reason 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 niix'it, tiie sip will flow the next day, as the vitality 

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



Section 8. Cyclosis. 



185. In the cinenchyma, there has recently been discovered 

 a circulation distinct from the two we have noticed, and called 

 cyclosis, the term we presume derived from Kuklos a circle. 

 The onlv intelli;;i!>'e account we have seen of this circulation 

 is from Pr«»f. Lindley. 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 lakes place ; the circulating fluid being 

 generally, though not alwaysa milky substance, and is called/a- 

 tex. The latex which conveys granular matter, circulates 

 through a plexusof reticulated vessels in all directions ; when the 

 vessels are pirallfl, an I near each other, the currents rise in 

 some, and fall in others, but, in connecting or lateral vessels, th^ 



1-2* 



