24 



ing distended, and they again are prepared to go through the periodic 

 performance of those functions which nature has assigned to them. 



Other instances of this kind are found in the lowest tribes of Algas, 

 as in the Gloiocladea, which also will resume an apparently fresh state- 

 even after being dried for years. 



One of the most beautiful however is to be seen in the Lycopodium 

 lepidophyllum from Peru, where moisture has the twofold effect of ex- 

 panding the contracted plant, and stimulating its dormant vitality. 



Numerous are the instances in which moisture exerts similar effects 

 which could be mentioned ; but enough have been brought forward to 

 illustrate the fact. 



Examples where moisture causes closed seed-vessels to open are 

 not so numerous, but Decandolle mentions that Defrance has observed 

 that the seed-vessels of Epilobium, and some other genera of the Ona- 

 gracece (Evening Primrose tribe), expand when saturated with mois- 

 ture and close when dry ; which fact I have found to be correct in 

 some respects. The seed-vessel of the Mesembryanthemum or Fig- 

 marygold exhibits also, we are told, the same phenomenon. 



The instances where the dryness of the tissues or the abstraction of 

 moisture causes a separation and an opening of the cavities of seed- 

 vessels and other organs, are exceedingly numerous ; and some of the 

 most beautiful contrivances have been contemplated by nature to per- 

 form various functions consequent on the changes these organs under- 

 go, when the aqueous contents are abstracted from their tissues by 

 that law which is impressed upon them, and operates in the season 

 of the maturation of the fruit 



To bring forward instances of this nature, I shall select only the 

 most common examples in which the effect of dryness in the tissues 

 has the property of preparing the way for the dispersion of the seeds. 

 If a poppy-capsule be examined when ripening, numerous valves or 

 trap-doors can be discovered beneath the radiated crown, which are 

 intended to give exit to the numerous seeds within. If the ripened 

 seed-vessel of the Rhododendron, or that belonging to any of the spe- 

 cies of Dianth us, Silene, Cerastium, Geranium, Erodium or Carda- 

 mine be examined, there will be found beautiful contrivances in all 

 these for effecting the dispersion of the seeds by loss of moisture. 



In all these examples this act is performed gradually and silently, 

 but in some particular plants it is accompanied by a very loud report, 

 and the seeds are violently ejected. This happens in many species of 

 Banksia, and still more remarkably in Hura crepitans, the sand-box 

 tree of the West Indies. 



