CIRCUMNUTATION OF SEEDLINGS. 



CHAP. 1 



on the following day with nearly the same result; and there 

 can be no doubt about the circumnutation of the hypocotyl. 



Primula Sinensis : conjoint circumnntation of hypocotyl and cotyledon, 

 traced on vertical glass, from 8.40 A.M. to 10.45 P.M. Movements of 

 bead magnified about 26 times. 



Cyclamen Persicum (Primulacese). This plant is generally sup- 

 posed to produce only a single cotyledon, but Dr. H. Gressner * 

 has shown that a second one is developed after a long interval 

 of time. The hypocotyl is converted into a globular conn, even 

 before the first cotyledon has broken through the ground with its 

 blade closely enfolded and with its petiole in the form of an arch, 

 like the arched hypocotyl or epicotyl of any ordinary dicotyle- 

 donous plant. A glass filament was affixed to a cotyledon, '55 

 of an inch in height, the petiole of which had straightened itself 

 and stood nearly vertical, but with the blade not as yet fully 

 expanded. Its movements were traced during 24 h. on a 



horizontal glass^ magnified 50 

 times ; and in this interval it 

 described two irregular small 

 circles; it therefore circumnu- 

 tates, though on an extremely 

 small scale. 



Stapelia sarpedon (Ascle- 

 piadeao). This plant, when 

 mature, resembles a cactus. 

 The flattened hypocotyl is 



Stapelia sarpedon : circumnutation 

 of hypocotyl, illuminated from 

 above, traced on horizontal glass, 

 from 6.45 A.M. June 26th to 8.45 

 A.M. 28th. Temp. 23-24 C. 

 Movement of bead magnified 21 

 times 



fleshy, enlarged in the upper 

 part, and bears two rudimen- 

 tary cotyledons. It breaks 



through the ground in an arched form, with the rudimentary 

 cotyledons closed or in contact. A filament was affixed almost 



* 4 Bot. Zeitung,' 3874, p. 837. 



