Yet man does recognise himself [as an animal]. But I ask you and the whole world for a generic differentia between man and ape which conforms to the principles of natural history, I certainly know of none... If I were to call man ape or vice versa, I should bring down all the theologians on my head. But perhaps I should still do it according to the rules of science.

A herbarium is better than any illustration; every botanist should make one.

If you do not know the names of things, the knowledge of them is lost, too.

It is not God, but people themselves who shorten their lives by not keeping physically fit.

If a tree dies, plant another in its place.

The species and the genus are always the work of nature [i.e. specially created]; the variety mostly that of circumstance; the class and the order are the work of nature and art.

Natural bodies are divided into three kingdomes of nature: viz. the mineral, vegetable, and animal kingdoms. Minerals grow, Plants grow and live, Animals grow, live, and have feeling.