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THE CONDITION FOR THE DISTRIBUTION OF PLANTS. 111 
Only lately I noticed that the spores of an aquatic fern brought from 
Rutnagherry, a species of Ceratopteris, germinate and form their 
prothallium on the lower portion of the plant. 
Many plants principally owe their distribution to other parts than 
to seeds, which then occasionally fail to come to perfection. Such 
plants areas arule much more difficult to destroy than seedlings. 
The parts which serve to distribute the plants are, in such cases, 
bulbs, tubers, rhizomes, but principally stoloniferous roots, as in many 
common grasses, as Cynodon dactylon, Sporobolus diander, Chloris 
barbata, Dactylis lagopoides, &c., or rooting stems or runners, as in 
Hydrocotyle asiatica, H. rotundifolia, Ozxalis corniculata, Ipomoea 
biloba and I. aquatica, Lippia nodiflora, &c. Rarely the flower stem 
is creeping and gives rise to new plants, asin the not uncommon 
Launea pinnatifida. Among Indian plants a few reproduce 
themselves by parts of the leaves, as Bryophyllum calycinum. 
All the artificial means of propagation are founded on the fact 
that every part of a stem or leaf has the power of forming a new 
plant, when brought under favourable conditions, and I think they 
are too well known to require mention here. 
But in considering the means of artificial propagation, it is only 
natural to think of cultivation as a cause, and a very important 
one too, of distribution of plants. By this not only a vast number 
of economical and ornamental plants have been distributed over the 
whole globe, but many plants have also unintentionally been natu- 
ralised in foreign countries as followers of cultivated plants. In 
regard to cultivation I may venture to say that in no other branch 
of natural science have so successful and astonishing results been 
obtained through the influeuce of man. The prosperity of most 
countries does in fact to a great extent depend upon cultivation, and 
I do not think I exaggerate when saying that by far the greatest 
part of the enormous Indian trade is due to cultivation, all the 
principal articles of export being vegetable products. 
Such astounding results have however not been obtained with- 
out labour, the object of which bas been to create better varieties, 
partly by selection and partly at the cost of extinction of the natural 
means of protection and adaptation for distribution found in the- 
original plants. 
Great successes in cultivation have been achieved in India, but 
I do not think that it is sufficiently appreciated that such results 
are frequently in the first instance due to experiments in botanical 
