LENGTH OF THE DAY. .35 



(iiemerocallis fulvci) opens at five in the morning; 

 the leontodon taraxacum, or common dandelion, 

 at five or six ; the hieracium latifolium (hawk- 

 weed), at seven ; the hieracium pilosella, at eight; 

 the calendula arvensis, or marigold, at nine ; the 

 mesembryanthemum neapolitanum, at ten or eleven : 

 and the closing of these and other flowers in the 

 latter part of the day offers a similar system of 

 hour marks. 



Some of these plants are thus expanded in con- 

 sequence of the stimulating action of the light 

 and heat of the day, as appears by their changing 

 their time, when these influences are changed ; 

 but others appear to be constant to the same 

 hours, and independent of the impulse of such 

 external circumstances. Other flowers by their 

 opening and shutting prognosticate the weather. 

 Plants of the latter kind are called by Linnaeus, 

 meteoric flowers, as being regulated by atmos- 

 pheric causes: those which change their hour 

 of opening and shutting with the length of the 

 day, he terms tropical; and the hours which they 

 measure are, he observes, like Turkish hours, 

 of varying length at different seasons. But 

 there are other plants which he terms equinoctial; 

 their vegetable days, like the days of the equator, 

 being always of equal length ; and these open, 

 and generally close, at a fixed and positive hour 

 of the day. Such plants clearly prove that the 

 periodical character, and the period of the 



