138 LIGHT. 



into higher latitudes, from equatorial regions, and keeping them 

 in an atmosphere, at the temperature of their natural situations, 

 by means of the hot-house, they flourish during the summer; 

 but during the short days, and long nights of winter, they droop, 

 exhibiting their suffering from the due influence of the solar rays. 



261. Raspail's theory above noticed receives confirmation 

 from the fact, that those vegetables which consist entirely of cel- 

 lular substance, are produced only in the absence of the light of 

 the sun, such as mushrooms, <fcc, their growth ceasing at the 

 coming of light. And it is a common notion among gardeners 

 that melons, cucumbers, and like pulpy fruits, increase much 

 more at night than during the day. Although Fungi grow only 

 in darkness, they will never produce spores capable of germina- 

 tion, without the action of the sun's light, and in cases where 

 the light of day never enters, there may be Fungi, but they 

 never increase or perpetuate themselves by the production of 

 spores. 



262* It is during the direct action of the sun's rays, and by 

 their agency, that the most important vegetable products are 

 generated. It is by their influence that water and carbonic 

 acid are decomposed, the oxygen being mostly liberated, and 

 the elements combining in other proportions, for the formation 

 of the various oils, resins, &c, including the most important and 

 abundant of the vegetable products. What is generally termed 

 the sleep of plants, that is, the folding up of compound leaves, 

 and the closing of flowers, is, no doubt, in most instances, occa- 

 sioned by the want of the stimulating action of the solar rays ; 

 for we see leaves and flowers, that were folded up during the 

 night, expand with the first rays of the morning sun. 



263. We have upon record many instances of the singular 

 phenomena of flowers during twilight emitting flashes of light. 

 It is said the daughter of Linnaeus first observed this emission, 

 exhibited by the Tropckolum Majusor Garden Nasturtium. The 

 flashes occur only during twilight, in the morning or evening; 

 those of the evening being much the most brilliant. The plants, 

 from whose flowers these flashes have been observed to issue 

 most frequently, are the Marigold, Calendula officinalis, Orange 

 lily, Lilium bulbiferum, African marigold, Tagetes patula, and 

 Sunflower, Helianthus annuus ; but Mr. Trimmer, in an article 

 in the 2d vol. of "Paxton's Magazine of Botany," p. 193, ob- 

 serves that he had observed it in many other flowers. 



H. w is it in high latitudes ? — 261. What confirms Kaspail's theory ? How 

 w ; tr Fungi ?— 262. What is accomplished by the direct action of the sun'a 

 raya ^--263. What examples of flowers' light? 



