Propagation by Cuttings. 199 
With very few exceptions, of which the greenhouse smi- 
lax * is one, cuttings of the succulent growth of the stem, 
with a certain amount of healthy leaf surface intact, will 
develop roots in all plants, under proper conditions of humi- 
dity and temperature; hence propagation from green cuttings 
is a very common and expeditious method of multiplying 
plants. The healthy leaf surface, capable of assimilating 
fuod, is a very important part of a green cutting, because 
the stem is less abundantly supplied with reserve food 
during the growth period than during the dormant period 
(185). 
Since the presence of leaf surface upon the cutting 
greatly promotes transpiration (75), propagation from green 
cuttings is scarcely practicable in the open air. The cold- 
frame, hotbed or propagating bed is essential to furnish 
the needed conditions of humidity and temperature. Bot- 
tom heat, with a comparatively low atmospheric tempera- 
ture, is especially important with green cuttings, in order 
that the food assimilated in the leaves may be devoted to 
the formation of roots. A small leaf surface on the cutting 
is generally preferable to a larger one; in many plants, a 
portion of a single leaf is sufficient. The leaf surface on 
the cutting should in no case be permitted to wilt, hence 
cuttings should generally be sprinkled with water as soon 
as made. 
378. Especial Care is Necessary in Propagating 
plants from Green Cuttings. In planting the cuttings, the 
material of the propagating bed should be put in close 
contact with the stems,and no leaves of the cuttings should 
be covered. Since roots cannot grow without oxygen, the 
bed must not be so freely watered as to exclude all air from 
* Asparagus medeloides. 
