64 
ADVENTITIOUS ROOTS 
(INCLUDING NOTES ON STILT-ROOTS, LENTICELS, PNEUMATOPHORES ; 
SWAMP PLANTS.) 
Adventitious roots are roots arising from steins or leaves. The rarer phenomenon 
of developing adventitious roots on leaves is taken advantage of to a small extent in 
horticulture, and need not be further referred to here. In practice all dicotyledons, 
and most monocotyledons, given favourable conditions, which can always be forced 
by the various horticultural methods of cuttage, can be made to produce this phenomena 
of root action. 
It does not matter whether the material for the purpose is selected from the stem, 
root, or leaf from growing wood, as in Euphorbia, or ripened wood, as in Scdix; from 
short pieces of root, as in Bouvardia, or long pieces, as in Rubus (Blackberry), or from 
the leaf, entire as in Echeveria, divided as in Begonia, or from bulb scales, as in Lilium. 
In all these cases roots can be produced without the aid of the radicle from the seed. 
Stilt-roots. Some adventitious roots are, for obvious reasons, called "Stilt- 
roots," " brace-roots," " prop-roots." 
Stilt-roots are attached to the main trunk, being developed from the lower part 
of the stem, to which they are attached obliquely and stilt-like. These are well-known 
in the case of the Screw Pine (Pandanus) and certain Mangroves of our coasts, which 
are useful in fixing mud-banks. They are common in Maize (Indian Corn). 
We have also spinous and non-spinous adventitious roots on Palms. Verschaffellia 
splendida H. Wendl. is a good example. The root-system often consists of a succession 
of roots produced farther and farther from the original base of the stem after the dis- 
appearance of the ordinary or tap-root. Some Palms and Screw Pines are ultimately 
borne several feet clear of the ground, in consequence of the lower ones dying away, by 
the stout adventitious roots which succeed each other higher and higher up the trunk. 
We notice this form of Stilt-root in certain Orchids in our glass-houses. For example, 
Aerides odoratum Lour., Angraecwn eburneum Bory, Vanda teres Lindl. 
Common Aroids illustrating this phenomenon are Alocasia macrorrhiza Schott., 
Philodendron Andreanum Devans, Anthurium ornatwn Schott. 
In quite a number of well-known economic plants we have adventitious roots. 
For example, in the Onion, the single primary root lasts but a short time, and is succeeded 
by others, which do not arise as branches from the primary one, but spring from the 
very short stem of the plant. In the case of wheat and barley, when the plants have 
begun to unfold a few leaves above the ground, the primary roots are succeeded by 
