Influence of Artificial Light on Vegetables. 189 



flower at a certain hour, and perifh at a certain determined 

 period, which never exceeds twenty-four hours. The marvel 

 of Peru (mirabilis jalapa) when expofed to the light of the 

 lamps for three days, continued to open in the evening, and 

 to clofe together in the morning, nearly at their accu'iomed 

 hour. The cafe was the fame in total darknefs ; but, being 

 expofed to the light of the lamps during the dav, they firft 

 exhibited fome irregularities, but on the fecund day they 

 opened in the morning and clufed up at night. The con- 

 'volvulus purpureas, which unfolds itfelf in the opencR air at 

 ten in the evening, having been expofed to the light of the 

 lamps, opened the lirft day at ten in the evening, and next 

 day at fix. 



The rock-rofe, broad-leaved tree-prim rofe, bind- weed, ficoi- 

 des, marygold, and the diarapndfig-marygojd, exhibited a great 

 number of variations mentioned by C. Decandolle, which it 

 would be too tedious to detail here. We fhall only add, that 

 the Egyptian fig-marygokl [mefcmlryantbemum nocliforuni), 

 when expofed to light during the night-time, and to obfeu- 

 rity during the day, opened in the morning and clofed them- 

 felves at night ; and that the mej'cm' : rya.ntbemu.m fplcinhns 

 and tenuifoiium, expofed to a heat of 6c/, opened their 

 flowers in a very fhort time, while the fame heat had no 

 influence whatever on other plants. 



Bonnet, who has endeavoured to explain the deep of 

 plants, fuppofes that the lower fupface of the foliele, fuch as 

 thofe of the take acacia for example, is fufccptible of ex- 

 tending by moiflure, and that its upper furface is fufccp- 

 tible of extending by drynefs. But C. Decandolle obferves 

 that the moving caufe feems to act on the inlertion of the 

 fotiole, and not on the entire furface; that this explanation 

 cannot be applied to the leaves the Joliolc of which inclines 

 forwards or backwards ; and that it would be neceflary to 

 admit that the fop bora and the gu'ihnul'ina, which in the night 

 throw down their leaves, are organised in an inveri'e manner 

 to the falfe acacia; which is not confirmed by anatomy. The 

 caufe of the deep of plants is therefore really unknown. 



Ii; none of the experiments was there any change made in 

 the progrefs of the oxalis jlr'icla and incarnata, but a power- 

 ful 



