Nine times out of ten when we speak of "tropical vegetation" the chief idea in our mind is luxuriance of foliage, rather than any particular leaf form. I realized this during my first day in England, when I saw clearly that the overwhelming beauty of England is due chiefly to her great luxuriance. For when the earth seems teeming with fertility, everything looks prosperous and happy. America does not yet have this look, except in spots. One great reason for it is that hitherto we have relied chiefly upon European plants and these, broadly speaking, do not fit our climate as well as our own and those from China and Japan. Throughout this book I have been illustrating in many different ways a single theme, viz., that America can never get this happy, prosperous look, this "nearly tropical luxuriance," until American plants constitute the bulk of our plantings.

We must have a little "spice," however, and my present object is to explain the different ideas that roam about in consciousness when we speak of "tropical effects" or "tropical charm".