Observations on the daily growth of Wheat and Barley. 155 



that it may even be followed by the eye, and is much quicker 

 during the day than during the night. 



The stem of bulbous plants, which only bear at their summit 

 a single flower, or a single bunch of flowers enveloped in a 

 spatha, is without doubt the organ best suited for observations 

 of this kind, not only because its growth is very rapid, but also 

 because the bulb presents a fixed base, and the origin of the 

 spatha a determinate summit. But as the author was sensible 

 that no important result could be obtained otherwise than by 

 the comparison of a pretty large number of observations made 

 in nearly similar circumstances, and as he could not easily pro- 

 cure a suflicient number of individuals of this kind, he resolved 

 to make his experiments upon gramineag, and consequently 

 upon leaves. 



After planting in flower-pots seeds of loheat and barley, 

 which he placed three and three in each vessel, he selected for 

 his experiments four pots, containing six plants of wheat and 

 barley, which appeared to him the nearest to each other in size. 

 These vessels were placed in a very light room, heated once a 

 day at six in the morning, by means of a large earthen-ware 

 stove. The shutters of the apartment were hermetically closed 

 every evening, and were opened again at day-break. A 

 Reaumur's thermometer, placed near the window at the height 

 of the vessels, marked the temperature of the apartment, and 

 was consulted each time that the plants were measured. 



The observations commenced on the 11th March, at eight in 

 the evening, and continued till the 16th March, at eight in the 

 morning. During this period of five nights and four hours, the 

 weather was in general cloudy and soft, and the sun appeared 

 only on the morning of the 1 4th. The external temperature of 

 the atmosphere, of which the author gives a table, presents the 

 following general result : 



At 7 in the Morning. At 3 in the Afternoon. 



Max. Mln. Max. Min. 



+ 2". _0°.25. +4.''00. +1°.45. 



The temperature of the apartment never rose above -)- 17°.50, 

 and never fell below -\- 14°.0() ; which gives a mean of -\- 15°. 75. 

 The author also gives a table of the state of the temperature of 

 the room for each observation ; and remarks that the gradual 



