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Scientific Memoirs by

a wide-spread species that probably only occurs in India as a cultivated plant,
and is very generally planted throughout the Malay Archipelago, North Australia,
Polynesia and Africa,¹mainly for the dye-stuff yielded by its roots. But the
Laccadive plant is not true M. citrifolia, but that variety which Dr. Roxburgh
considered a distinct species and named M. bracteata. This plant is confined
to India, Ceylon, and the Andamans, is perhaps oftener wild than cultivated,
and was, where Mr. Hume found it, certainly wild. Unless then it be assumed
that this plant has here escaped from cultivation, and that its cultivation has
been at the same time given up, the species must be looked on as an example of
a sea-introduced plant. Mr. Hemsley ("Challenger " Reports; Botany, Introd.,
p. 43) contends for an ocean-distribution for true M. citrifolia, and the evidence
from this variety certainly supports his view.

     Plumbago zeylanica is a common plant in indian gardens,and, besides being
grown for its appearance, is used in Indian domestic medicine in skin diseases.
It has therefore probably been introduced intentionally. At the same time it is a
plant that readily throws itself out of cultivation, and it may have reached the
Laccadives only as a weed.

     Calotropis gigantea may have been intentionally introduced. Its milky
juice is medicinal, and it yields an excellent fibre used along the western coast
of India. At the same time it is a common road-side weed everywhere on the
mainland, and it may be as a weed that it has reached the islands, while there is
nothing to have prevented its seeds from having been brought from the mainland
by winds. Then both Cynanchum and Tylophora may have been introduced on
account of their juice, since they too are Milk-weeds; it is, however, far more pro-
bable that they have reached the islands with the assistance of wind.

     The large-flowered Ipomœa may have been intentionally introduced, or more
probably perhaps, have arrived as a weed. At the same time the seeds of several
species of Ipomœa occur frequently in ocean-drifts, and some are characterized by
the readiness with which they become distributed by ocean-currents. To
strengthen this possibility we have here the fact that Mr. Humefound the species
in Betrapar, which is one of the uninhabited islands. On the whole then this
species is more probably sea-distributed, though the mere fact that it occurs
where there are no inhabitants does not render the evidence conclusive; since the
island is visited by the inhabitants of the other islands of the group, and since
it does not follow, because Betrapar has no permanent inhabitants now, that
this has been always the case.

     The Datura may have been introduced purposely, for it is not infrequently
deliberately cultivated by evil-disposed people. It is, however, a common Indian
weed, and has probably been only unintentionally introduced.

      ¹Mr. Hemsley ("Challenger " Reports; Botany, vol. i, part iii, p. 109) gives America also.