Cyi 



LETTER XXXI. 



only in a dry soil that they are capable of vegetating. 

 Nature, therefore, gives this plant the power, by virtue 

 of its hygrometrical quality, of keeping the seed-vessel 

 fast shut up while exposed to damp, and it is only 

 when it finds itself in a dry station, fit for the dissemi- 

 nation of the seeds, that the valves contract and open 

 sufficiently to allow the latter to escape. It is impossi- 

 ble to imagine a more obvious interposition of Provi 

 dence than this is, for securing the preservation of the 

 race of the Mesembryanthemums. 



But it is only one out of hundreds, that might be 

 adduced to show the evident design that is visible in 

 this part of the creation ; and, what is not less curi- 

 ous than interesting, where it is necessary for plants 

 to disperse their seeds in the damp, nature provides 

 for this also, with the most admirable certainty, by 

 giving the valves of the seed-vessel the power of 

 opening in humidity ; and so employing the same kind 

 of power, that of hygrometrical action, for two opposite 

 purposes. Thus, to use the words of the learned M. 

 De Candolle, the Evening Primroses open the valves of 

 their pods in wet weather, and close them when dry. 

 This circumstance is probably connected with the 

 manner of life of these plants, which naturally flourish 

 in swampy places, and require to sow their seeds 

 when the weather is wet. This notion is confirmed 

 by the histoiT of another plant having the same pro- 

 pertv, namely, that singular Eastern herb, known 

 under the strange name of Hose of Jericho (Anasta- 

 tica hierochuntica). This grows in the most arid 

 deserts. At the end of its life, and in consequence 



