134 Bower —On the limits of the use 
those terms. If, in pursuing this subject, I traverse ground 
which is too familiar for the taste of some, the excuse will be 
that this is done in the interest of clearness. 
Sachs has stated in his Lectures 1 that ‘it is impossible to 
express morphological ideas clearly and exhaustively by 
means of simple definitions . 5 Since the definitions cannot 
be simple, it is all the more necessary to be aware of, and 
to estimate at their true value in relation to one another, 
those criteria upon which organographical distinctions are, or 
have been, based ; these will now be considered seriatim, 
and with special reference to the distinction of the parts of 
the shoot, viz., axis and leaf. 
I. The first basis of distinction of the parts of plants was 
undoubtedly that of external form and appearance , and it is 
also popularly used to the present day by the lay public, 
which would call underground stems roots, and the phyllo- 
clades of Ruscus leaves. It is unnecessary here to show that 
the external form and appearance of the mature member form 
an insufficient basis for morphological distinction, since this 
principle is insisted on in every text-book. 
II. Nor is it necessary here to point out, or prove by 
examples, that function is an unsafe guide. It may, however, 
be noted in passing, that function has been made the chief 
basis of the system of physiological organography propounded 
by Professor Sachs in his Lectures ; and though he expressly 
states that his system is not intended to replace purely 
formal morphology, there can be little doubt that his use 
of familiar terms in a new sense will tend to obscure their 
morphological meaning in the minds of many. 
III. A method of distinction of members according to the 
disposition of the tissues in the mature state (the anatomical 
method ) is one which has especially met with acceptance in 
France, where it took its origin and was first developed in 
the extensive researches of Van Tieghem 2 . This author 
1 Engl. Ed. p. 2. 
2 Recherches sur la Symetrie de Structure des Plantes Vasculaires, in Ann. ScL 
Nat., ser. 5, t. xiii. 
