130 Otis F. Curtis 



the pot is usually lower, due to the cooling effect of evaporation. Bailey 

 suggests further that the deflection of nutrients ("plant food") to that 

 region, due to evaporation, may increase growth. The experiments 

 reported here, however, would contradict this. The more probable 

 explanation, which Bailey also suggests, is that the soil is better aerated 

 in that region. This may explain also the matting of roots next to the 

 walls of the pot in the case of potted pla,nts. 



A practice commonly followed in the propagation of dormant cuttings 

 from woody varieties is that of burying the cuttings for a time with the 

 basal ends upward. Various reasons for this practice have been offered. 

 It has been said that sap naturally flows upward, and therefore, if the 

 cuttings are buried with the basal end up, the sap will flow into that 

 part and form roots. Other reasons assigned are that the tops are thus 

 kept dormant, or that the bottoms are thus directly heated (Bailey, 

 1913:57). It is questionable whether, at the time of year when the 

 cuttings are thus buried, the temperature near the surface of the soil 

 would be higher than that a few inches below. It is conceivable, how- 

 ever, that during the warm days in spring the temperature at the surface 

 may exceed that below. It would seem that a very possible explanation 

 might he in the fact that twigs so treated would have much better aera- 

 tion at the basal ends than if buried in an upright position. 



Bottom heat is as a rule beneficial to root formation and is very neces- 

 sary in the propagation of some varieties. This increased temperature, 

 of course, tends to increase respiratory activity in those tissues that 

 produce roots. The upper part of the stem, on the other hand, is left 

 cool and remains in a comparatively quiescent state. When the tem- 

 perature is approximately equal thruout the length of the stem, the tops 

 of many varieties will develop and root formation is then inhibited. The 

 higher temperature may serve also to decrease the retarding effect of 

 any carbon dioxide that may be present. Such an effect on the germination 

 of seedlings has been shown by the work of Kidd (1914). 



It has been shown that the stimulation resulting from treatment with 

 potassium permanganate is largely independent of any effect on the rest 

 period of the twig. Nevertheless it is fairly clear that better results will 

 be obtained with most woody cuttings if these are taken before the rest 

 is over. As a general rule, woody cuttings are taken in the autumn before 

 heavy frosts or freezes set in (Bailey, 1913, and Sim, 1904). One of the 



