Epinasty and Hypouasty of Raphamis Cotyledons. 365 



NORMAL CONDITIONS. 



For purposes of comparison let us first note the growth of 

 the organs selected when exposed to ordinary conditions of 

 strong illumination on a shelf in plant-house. 

 After 24 hours. Seeds swollen, but cotyledons not leaving seed coats so 



that no observations could be taken. 

 After 48 hours. Cotyledons have left the seed coat. The lower and larger 



are strongly hyponastic, fiwhile the inner and upper ares trongly epi- 



nastic. Slightly turned downward. 

 After 72 hours. Upper cotyledons slightly hyponastic, both now being 



curved outwards : i. e. both hyponastic. Not separated. 

 After 96 hours. Cotyledons separated, owing to the epinastic curvature of 



the hypocotyls. Strongly epinastic, upright. 

 After 120 hours. Cotyledons epinastic, separated. Plants i inch high. 



It is interesting to note with regard to these that if one ob- 

 serves them early in the morning they are nearly always slightly 

 hyponastic, especially if the weather is dark or cloudy. Later 

 in the day, {i. e. 9 to 10 o'clock) they are found to be epinastic. 

 The organs with which we have to do are evidently very irrita- 

 ble. 



B. 



SPECIAL CONDITIONS. 



The special conditions may now be followed in the order 



of experimentation. 



I. Diffuse daylight. — This was secured by selecting a con- 

 venient place under the shelves of the plant-house, sheltered 



from the rays of the sun and the reflection from the glass roof. 



After 48 hours. The same phenomena are to be noted as in A, but less vig- 

 orous ; cotyledons less opened, turned downward. 



After 72 hours. Curvature less than in A. Cotyledons parallel, turned 

 downward. 



After 92 hours. Cotyledons most of them upright and parallel. The 

 upper has overcome its epinasty and become slightly hyponastic, while 

 the lower is still slightly hyponastic. Sometimes slightly epinastic, 

 often straight. 



After 96 hours. Cotyledons hyponastic. Not separated. 



After 120 hours. Cotyledons hyponastic. Not separated. 



After 144 hours. Cotyledons hyponastic. Separated 



After 168 hours. Cotyledons hyponastic. Unchanged. 



2. Total Darkness. — Using boxes placed one within the other 



