524 SECTIONAL TRANSACTIONS.—M«. 
to have a definite polarity in the sense that the development of cambial activity is 
always in a basipetal direction from the base of the lateral members of the developing 
shoot. 
The basipetal differentiation of new tissues from the cambium, particularly of 
the phloem, would seem to be closely connected with the movement of food substances 
in the same basipetal direction and would also seem to be largely responsible for the 
phenomena of polarity observed in cutting propagation. This standpoint seems to 
be supported by observations upon cuttings of Coleus in which, when the original 
vascular strands from the leaves upon the cutting have been severed, basipetal differen- 
tiation of new ‘ commissural’ vascular strands has followed. 
Mr. L. B. Srewarr.—The Propagation of Leaves, Monocotyledons and 
Dicotyledons. 
In Gesnerads the propagation of leaves is very simple. In Gloxinia and Gesneria 
the first thing that takes place is the formation of tubers, these being the stem of the 
plant, any offsets which they may send on afterwards being yearly growths. These 
tubers give buds and make an annual root growth. When the plants grow older the 
tubers attain some considerable size and give a free condition of flowering. 
In Alloplectus there is no tuber formation, and a mass of roots is formed at the 
base, and the stem is thrown up into the air. In many of these plants the amount of 
tissue in the leaf controls the offspring. By using a whole leaf one gets nearer 
an adult plant than if one severs the main veins when juveniles are formed, but in 
Alloplectus, although one takes a whole leaf, juvenile leaves always form at the base 
of the bud-growth first. 
In the Melastomads, which are plants which have pleurocostate venation, if a 
large number of plants are wanted it is necessary to sever the main veins. 
In Phyllagathis rotundifolia, where the leaf is much dissected, the young plants 
have exactly the same kind of leaf as the seedlings, t.e. very hairy. At the same time 
they take a considerable period before they drift into the adult stage. Where 
juvenile forms are got on leaf cuttings, sometimes the stage of transition is lengthy, 
but this depends entirely on the height of the plants and the manner of their 
growth. Plants of the Melastomads are interesting in their root formation, having a 
very red root tip which is enclosed in a globe of mucilage. One seldom finds that 
young plants with juvenile characteristics flower well until they reach the adult 
stage. 
ir many of the Acanthads such as Sanchezia nobilis, Ruellia and Acanthus, the 
food material in the leaves descends very quickly to the cut surface, and they are 
exceedingly easy to root. Bud formation of some of these leaves is rather marked. 
Many buds may be formed and one or other of the buds take up the dominant factor 
and the rest of the buds are left in a recessive state until such time as an accident may 
occur to the growing point when one or other of the buds will then take up the 
dominant position again. 
In Begonias and some of these other plants, it is not necessary to keep entirely 
to the blade of the leaf for their propagation. Some Begonias which have a con- 
siderable leaf stalk, can be propagated easily from the leaf stalk alone. 
The propagation of the Rose, although not a commercial proposition, can be 
done easily by leaves. Although rooting takes place in a very short time, if the leaf 
has not made buds and formed its growth before the winter comes on, there is con- 
siderable difficulty in carrying them right through the winter to the following spring, 
because at that particular time the activity of the roots is low. p 
Many of the Legumes can easily be propagated from the leaf, more especially 
some of the annuals and herbaceous plants. In Brownea, which plant can be rooted 
easily, three or four years may elapse before the root stalk gets sufficient nourishment 
instilled into itself and is able to make bud formation. After the buds are formed, 
the young growth shoots up into the air and for a portion above the soil makes only 
scale leaves before the formation of ordinary foliage leaves. 
Dicotyledonous plants which have thick fleshy leaves are easy to propagate, 
because they have a liberal supply of food material at their disposal, e.g. Sedum, 
Crassula and Bryophyllum. 
Monocotyledonous plants can be increased very rapidly by leaf propagation. By 
severing the leaf of Sanseveria, which is of economic value, into several portions, each 
part of the leaf gives off a plant, and sometimes many plants. 
