8 
are practically produced in their native country aJone develop, no 
more being produced. Japanese azaleas behave in jnuch !ne same 
way, but some plants have continued to flower a little annually. In 
plants which behave in this way a strain might be obtained winch 
would flower as nearly as well as in cold climates by careful selec- 
tion. Certain shrubs after some time when wed grown produce a 
few flowers, on new wood and then cease to flower again. Tibouchina 
semidecandra , a native of Brazil, was obtained from Kew a few years 
ago as a small plant. It grew strongly and attained a height ot 
about six feet, and was propagated by cuttings, of thjese; two plants 
produced their fine flowers once or twice and then^ eased to flower 
altogether. It has apparently done so betore, for in the Herbarium 
is a specimen from a cultivated plant prepared by Mr. Cantley, 
but the plant had long ceased to exist in cultivation here, doubtless 
for the same reason. 
The two abutilons of Christmas Island, raised froin seed brought 
myself, {A. and A. Lister i) grew to a great, size fully as 
healthily as any I saw in their native home. Both , have flowered 
but very sparingly, much more so than in Christmas Island. The 
locality they inhabit is very xerophytic, and most of the local plants, 
ferns excepted have failed to grow at all in our wet climate. 
Many exotic shrubs, however, flower very well and abundantly 
but never set fruit ; such are Bigoma magnified , B. oequinociialis , 
Tecotna ceramensis , Od&ntadenia speciosa , Mussaenda eryth.ro- 
phylla, Bougainvilleas , Tecyna Curtisii, Ipomea arbor ea, Allamanda 
Cathartica (A. schottii aid A. 'williams i fruit regularly) and 
Solanum maronieuse which has been already mentioned the causes 
of these failures to fruit are not very clear. Some of the causes have 
already been suggested, but there are many cases in which the 
reasons are not obvious, as. the reproductive organs are complete 
and healthy and the plants regularly visited by insects. A plant 
introduced from other countries frequently does not fruit the first 
year apparently because it is not visited by insects, who do not seem 
to find it out at first, bubafter a year or two it is regularly visited 
by insects and produces ftfiits. 
The question next arises as to how we can acclimatize exotic 
plants so as to make them available for the country into which they 
have been introduced. We know little as yet concerning the physi- 
ology and oecology of plants of the tropics. There have been but 
few researches made into this subject. The facilities for this work 
in the British Empire are very scanty, and there are nowhere labora- 
tories or scientists employed in researches of this kind such as are 
possessed by the Dutch at Buitenzorg or the Americans in Hawaii 
and the Philippines. Much good work on certain lines have been 
done in these establishments, but much of our knowledge of tropical 
agriculture remains in the empirical stage. 
By careful selection we may obtain plants proof against the 
diseases which prevent their cultivation, and we may obtain strains 
suitable for cultivation under all classes of soil and climate. By 
