That trees belonging to all orders have their sexes more often separated than other plants, I find to be the case in this country; and at my request Dr.

Hooker tabulated the trees of New Zealand, and Dr.

Asa Gray those of the United States, and the result was as I anticipated.

On the other hand, Dr.

Hooker informs me that the rule does not hold good in Australia: but if most of the Australian trees are dichogamous, the same result would follow as if they bore flowers with separated sexes.