602 
PHANEROGAMS. 
chosen for the various separate organs, in order to render the explanation more readily 
visible to the eye. The leaves of the perianth are represented by arcs of a circle, a kind 
of mid-rib being indicated on each of the outer whorl of these, or calyx, merely in order 
to distinguish them at a glance from the inner whorl. The sign chosen for the stamens 
resembles a transverse section of an anther, but without reference to the position of the 
pollen-sacs or of their mode of dehiscence whether inwardly or outwardly. When the 
stamens are branched, this is indicated by the signs being grouped, as in Fig. 408, where 
the five groups correspond to five branched staminal leaves. The gynaeceum is treated 
as a simplified transverse section of the ovary, since it is thus most easily distinguished 
from the other parts; the marks within the loculi of the ovary indicate the ovules, 
which however are only represented in those cases where their actual position can be 
expressed by so simple a plan. The size, form, and cohesion of the separate parts are 
not taken into account at all. The construction of these diagrams is based partly on 
careful investigations of my own, but chiefly on the studies of Payer in the history of 
development (Organogenic de la fleur), as well as on the descriptions of other authors 
(Doll, Eichler^, and Braun). 
I draw a distinction between empirical and theoretical diagrams. The empirical dia- 
gram only represents the relative number and position of the parts, just as a careful 
observation shows them in the flower ; but if the diagram also indicates the places 
where members are suppressed — ^which can only be determined by the history of 
development and by comparison with allied species, especially if it points out relationships 
Fic;. 405 —Diagram of the flower of FIG. 4o7.^Diagt'am of the flower of FlG. 4o8.---Diag-t-am of the flower of 
Liliacece. Celastriis (after Payer). Hypericum calycumm. 
which are entirely the result of theoretical considerations — I call it a theoretical diagram. 
If the comparison of a number of diagrams shows that, although empirically different, 
they nevertheless yield the same theoretical diagram, this common theoretical diagram 
may be termed the type or typical diagram according to which they are all constructed. 
1 consider the careful determination of such types an important problem, the solution of 
which may be extremely useful in the classification of Angiosperms. When the type has 
once been ascertained, the theoretical diagrams which correspond to it may be treated 
as derivative forms from which particular members have disappeared, or where they have 
been replaced by a number of members. From the stand^point of the theory of descent 
the type corresponds to a form still in existence or that has already disappeared, from 
which the species to which the derivative diagrams belong have arisen by degeneration 
(/'. e. by abortion ^) or by multiplication of the parts. 
A few examples will explain this. The flower of Grasses, which is seated among the 
paleae, may be deduced, as is shown in Fig. 409, on the theory of the abortion of certain 
^ [Eichler, Blüthendiagramme, I, II, 1875-8.] 
^ The construction of the diagram itself shows that the theory of abortion is justified even 
where the earliest state of the flower-bud gives no indication of the absent member, if the number and 
position of the parts present point distinctly to such a hypothesis. If the idea of abortion in this 
sense is not admitted, neither can the increase in number of individual parts, or their replacement by 
several, be allowed. It is only the theory of descent that gives a rational explanation of either fact, 
and that a very clear one. 
