Medical Officers of the Army of India.
57
As, however, it is probable that many of these have reached the islands
independently of man's agency, while others, though introduced by man, may
have been brought unintentionally, it becomes necessary to analyse this list in
detail.
The Poon-spar, or Alexandrian Laurel, is (along with Barringtonia speciosa)
about the earliest species to appear on newly emerged uninhabited coral islets,
and primâ facie therefore might be looked upon as an ocean-distributed plant.
But on closer consideration the case is less clear. The tree is much cultivated
in India and is planted by the Laccadive Islanders, as it is by the people on the
opposite coast, to provide them with masts and spars. Then, not only is it
planted where it occurs, but it does not seemto occur on every island ( e.g. Dr.
Alcock did not observe it on Anderut, which is moreover the island nearest
India), and the species that elsewhere is so intimately associated with it
(Barringtonia) , does not appear to have reached the archipelago. So far then
as the Laccadives are concerned, it seems necessary to look on the Poon-spar
as a species introduced intentionally by man.
The case of the Portia tree (Thespesia) is identical. It also is a shore
species; its fruits occur in eastern tropical ocean-drifts, and it is widely distri
- b u t e d o n e a s t e r n t r o p i c a l s h o r e s . B u t i t i s , o n t h e o t h e r h a n d , a f a v o u r i t e t r e e
and is much planted, especially in Madras and in Ceylon, both on account of
its showy flowers and because of its tough and durable wood used in boat-
building. It only occurs on one island—that which has most intercourse with
the mainland—and it is there distinctly a planted species. Its intentional in
- troduction by man is therefore much more certain than even in the preceding in
- s t a n c e .
The common Cowhage (Mucuna pruriens) , to which Mucuna capitata is
closely allied, has a very wide distribution, and seeds of various species of
Mucuna have frequently been found in ocean-drift, and that too in a germinable
condition after having traversed wide intervals of sea. There is thus no in
- t r i n s i c r e a s o n w h y
M u c u n a c a p i t a t a
may not have been carried to the Lacca
- d i v e s b y o c e a n - c u r r e n t s . B u t , o n t h e o t h e r h a n d , t h i s p a r t i c u l a r s p e c i e s i s i n t h e
Laccadives, as it appears to be everywhere else, purely a garden plant; it there
- f o r e i s a l m o s t c e r t a i n l y a n i n t e n t i o n a l l y i n t r o d u c e d s p e c i e s .
With Cœsalpinia Bonducella the case is different. This is a widely dis
- t r i b u t e d t r o p i c a l p l a n t , w h o s e s e e d s o c c u r i n m a n y o c e a n - d r i f t s ; i t i s b e y o n d
doubt an ocean-distributed plant elsewhere; in the islands where it occurs it
forms a dense jungle. So, while it is just within the bounds of possibility that
it may have been introduced on account of the antiperiodic properties of its
bitter seeds, the probability is that it has been introduced by ocean-currents.
The evidence as to Morinda is not altogether clear. True M. citrifoliai s
J