1922-23.] BOTANICAL SOCIETY OF EDINBURGH 185 



Experiment I. — One of the bags was removed after fourteen 

 days, and five cuttings, 6 inches-12 inches (seven to twelve 

 internodes) in length were made, using the terminal portion 

 of the most actively growing shoots. These were placed in the 

 propagating pit, temp. 60° F., along with a control of similar 

 cuttings from a normal branch. Two days later it was found 

 that while the normal slips became flaccid and cast a con- 

 siderable number of leaves, the etiolated lost less turgidity 

 and no leaves, although during the time the shoots were in 

 the dark a certain percentage of leaves were shed. On the 

 sixth day callus formation was evident on the shortest etiolated 

 cutting, i.e. the youngest internode through which a cutting 

 had been made, and by the end of fourteen days the etiolated 

 cuttings had all with one exception formed callus. The con- 

 trols only showed callus in one case, and then only after twenty- 

 eight days, and to a very slight extent (fig. 1). 



Experiment II. — The second bag was left on for twenty- 

 eight days, and by doubling the time the branch was more 

 noticeably etiolated than in the first experiment, in that the 

 stems were winged, the internodes longer, the leaves reduced 

 in size and blanched. Terminal cuttings were made of the 

 etiolated and of the normal stems 4—6 inches in length, as in 

 the previous experiment, but this time the number of inter- 

 nodes was noted and never exceeded six, while those of the 

 first bag varied from seven to twelve. Callus appeared on 

 the fourth day onwards on 75 per cent, of the etiolated, and 

 two days later on the same percentage of the control cuttings, 

 but in subsequent development the amount of callus produced 

 on the individual etiolated shoot greatly surpassed that 

 produced on the normal. 



Experiment III. — Cuttings were made of the normal stem 

 at the 12th internode, with the terminal 4th-6th nodes re- 

 moved. These were placed in the propagating pit under an 

 inverted flower-pot with the hole closed. By the end of a 

 week callus formation was visible at the apices of the 

 cuttings, i.e. about the 4th or 6th internode of the whole 

 shoot (fig. 2). 



These experiments thus show that etiolation appreciably 

 hastens callus formation, especially in older stems ; that a 

 smaller proportion of the more etiolated branches form callus, 

 the optimum time of etiolation having probably been exceeded ; 



