CONDITIONS INFLUENCING REGENERATION. " 79 



CONDITIONS INFLUENCING REGENERATION OF THE HYPO- 

 COTYL IN LINUM USITATISSIMUM. 



MARY E. HEDDEN. 



(Abstract.) 



The experiments thus far performed have been to determine the con- 

 ditions governing the development of hypocotyl buds on Linum. 



Uninjured plants were first placed in a saturated atmosphere, but 

 only one out of twenty-five seedlings developed buds below the cotyledons. 

 In a dry atmosphere there were no buds formed. 



Next the cotyledons were cut off below their insertion when the seed- 

 lings were from 2-3 cm. high, and in nearly every case numerous buds 

 were sent out on the hypocotyl, under both dry and moist conditions. 

 The hypocotyl soon became very green and a slight callus covered the 

 wound. In the course of a few days numerous buds were developed. 



The origin of these buds varied according to the age of the seedling, 

 on a young hypocotyl they formed from base to apex, but on au old one 

 they formed only at the apex. There was no definite arrangement or 

 fixed law as to their appearance. 



The number of buds was also governed by the age, on young hypo- 

 cotyls from one to sixty buds Avere sent out, while on old ones never 

 more than three were formed. More buds were developed in a saturated 

 atmosphere than in a dry, and they developed more quickly in a high 

 temperature. ^ 



Numerous plants were placed in the dark, and at different tempera- 

 tures, but no hypocotyl buds were formed. The season also had a 

 marked effect upon the time of bud formation. The time for regeneration 

 during the fall and winter was from thirty to thirty-seven days, while 

 in the spring the}- regenerated in from seven to nine days. 



The experiments are still incomplete, but from the data thus far gath- 

 ered, it is evident that age, moisture, temperature, light, and season are all 

 important factors influencing the formation of hypocotyl buds. 

 Mary A. Hedden^ 



Botanical Laboratory, University of Michigan, 

 Ann Arbor. 



