1900-1901. | A Field Naturalists Holiday. 135 
_ of conservatories on either side of it. These conservatories 
_ were exhibited by hothouse builders, and contained in some 
cases interesting collections of plants,—one of cactuses, for 
example, struck me; but they are far too numerous to try to 
_ describe. We pass the greater and the lesser Palaces of Art. 
If we pause, however, in the space between them, and look 
_ over the new bridge, we shall see the most magnificent piece 
of city architecture in the world. On either side we have the 
_ permanent homes of art—which stand on the place of the 
Exhibition building of 1855—the Palais d’Industrie. The 
beautiful white stone of which they are constructed has been 
tinted with primrose and lilac so slightly as just to give it 
a feeling of colour, with the happiest effect. We leave the 
great avenue at the Pont des Invalides and go down towards 
the river. There we shall find in a little ravine a spot to 
delight the field naturalist. It is just at the side of the 
- foot-bridge which crosses the Seine. There is a collection of 
aquatics and succulent plants, opuntias and house-leeks, melo- 
cactuses and agaves and euphorbias, besides water-lilies and 
reeds and Egyptian papyri. We have here a picture—a 
tableau vivant—of how the plant suits itself to its surround- 
_ ings—the lilies and other aquatics living in water, the cactuses 
and the agaves reducing their leaf-surface as much as possible 
to prevent evaporation and economise water. We may notice 
amongst the plants a Euphorbia resenifera, which has very 
much the appearance of a cactus—although euphorbias and 
cactuses are a considerable way apart in the vegetable king- 
dom. The euphorbia has assumed the habit of the cactus to 
suit desert conditions. This little ravine, like so many other 
bits of the Paris Exhibition, is an object-lesson arranged with 
a deeper significance than a few rocks and pools with pretty 
_ plants might at first sight suggest. It is a thought-model of 
how the organism grows to suit the environment. 
We now come to the Palace of Horticulture, where all the 
_fruit- and flower-shows are held. These shows took place 
weekly, I think. Every week or so different lots of plants 
and flowers and fruits were exhibited. Once when the new 
supplies for the week had been brought in, I walked through 
the show. There were a great many asters of all colours, 
having the habit of Aster Tripolium. There was a striking 
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