ON THE HAIRS OF PLANTS. 5 



filled by a quantity of vessels shaped as at fig. 3. For seve- moisture in. ' 



ral years past I have attended with peculiar care to this phe- •^'^**"£^'-' 



nomenon, and noticed the sort of instrument used on the 



occasion. It never varies, and regularly appears to select 



the dew from the atmosphere. By four or five in the moni- 



ing they are almost empty; by eight, perfectly full; again 



emptied before noon, and late in the evening 1 have seen 



them replenished to bursting, or running over: but how 



they fill themselves, except by means of a vacuum, I have 



i\ot yet been able to discover. This year all the trees (or ra- Buds of trees 



ther the buds,] were covered with this vessel, owing; to the *^*^3^f^<^ w'lh 



'' . . occasional 



long drought in March, which never fails to bring it on ; it vessels. 



appeared as if all the buds were covered with diamonds. 



In peyfumed plants there is a species of instrument that Hairs of odori- 

 baffles all conjecture as to the manner of its management, or ^^^^^* plants, 

 the uses to which it is applied. This is represented at fig. 4. 

 e forms a part of it, but is often found separate. The diffe- 

 rent bells bubble between each division (when part of it is 

 turned to the sun) like a pulse glass^when a warm hand is 

 applied to one of the balls: on turning a very hot sun on 

 these, I once blew up two of them ; and it not unfrequently 

 happens, that the quantity within the hair, if heat is suddenly 



applied, bursts the vessels: but it is fortunate Avhen it does ,, . , 



t^^ _ ' Hairs always 



80, since they always break at the valve, and by this means break at the 



discover much of their interior formation. These instru- '*'^^®* 

 ments are mostly found in the balm of gilead, the most per- 

 fumed geraniums, and plants that coincide in this respect. 

 When 1 first saw this, and perceived the divisions to bubble, 

 I was persuaded it was a decomposition of water ; but was 

 soon undeceived, for none of it disappeared. 1 have since 

 repeatedly seen the effect, and been convinced, that it is si- 

 milar to that which takes place in the pulse glass, and caused 

 by the rarefaction of the air, and the increasing particles of 

 liquid from the admission of caloric among them. Indeed 

 every little power is visible here, nor can any instrument be Hairs uncom* 

 so fit to try every little variation of temperature, moisture, roon'y suscep-' 

 or evaporation^ as these most delicate diminutive ones, which alteration, 

 are never idle, as long as the vegetable on which they are 

 placed lives; sensible of every chaage, even Leslie's differ- 

 ential thermometer is quiet in comparison. 



Fig* 



