12 



MASS. EXPERIMENT STATION BULLETIN 435 



and root (3, 19) and this was here controlled bj- means of an automatic humidi- 

 fying unit^ sufplemented by judicious sprinkling of walks, walls and, less fre- 

 quently, the bench itself. 



The propagating bench, running east and west, was shaded on the south on 

 sunny days by white cotton cloth curtains the height of the greenhouse. If the 

 relative humidity can be kept high, constant shading is unnecessary and probably 

 undesirable; but if cuttings of white pine are watered from above while strong 

 sunlight is upon them, there may be some burning of the foliage and consequent 

 injur}' to the cuttings. 



Ventilation was kept at a minimum and used only when necessary to keep the 

 temperature down. The most favorable conditions for rooting cuttings of slash 

 pine have been found to include temperatures between 75° and 90°F. (19), and 

 in the work of the writer with white pine, air temperatures were allowed to climb 

 from a minimum of 70°F., at night, to about 95°F. on sunny days before ventila- 

 tors were opened at all. 



Figure 1. Rooted Cuttings of White Pine, 

 Taken in February and Piiotograpiied in May of the Following Year. 



Subsequent Growth of Rooted Cuttings 



A minimum requirement for a good white pine from the viewpoint of forestry 

 is that its trunk be vertical. It is correspondingly important to learn how rooted 

 cuttings of white pine behave in this respect, for not all rooted cuttings of all 

 conifers develop into straight and well-formed trees. 



Cuttings of yew grow into trees or shrubs with vertical trunks if the cuttings 

 are made from terminal shoots but the new growth ma>' be plagiotropic, the 

 trunk not vertical, if the plants grew from cuttings which were made from side 

 branches (10). Rooted cuttings of Douglas fir had not developed a well-defined 



^Standard Mode! No. 31 of the Standard Engineering Works. . 



