290 
The Ohio Naturalist. 
[Vol. XI, No. 5, 
have been adapted from older classifications. In this connection 
it might be stated that the Bentham and Hooker scheme of 
classification contains certain features which should not be thrown 
overboard bodily without due consideration. 
As stated in a previous article of this series, all possible char- 
acters and peculiarities should be considered in segregating 
groups. Gross and microscopic, and external and internal mor- 
phology, as well as embryology, physiology, and life cycle are 
important and must be taken into account if contradictions in 
supposed lines of descent are to be avoided. But when the groups 
have thus been established, one or at most, a very few definite 
characters in combination should give an exclusive definition. 
It will be evident to anyone, who has considered the subject 
in some detail, that the groups of monocotyls and dicotyls cannot 
be segregated on the basis of the flower alone, although the flower 
is perhaps the most important structure in the Anthophyta to 
indicate relationship. There may be apocarpous and syncar- 
pous, apetalous and choripetalous, monosporangiate and bispo- 
rangiate, and numerous other diverse developments in very 
closely related groups. From an evolutionary point of view, the 
starting-point of floral development must be sought among the 
homosporous and heterosporous Pteridophyta. The flower of 
the higher plants then seems to have come from a definite, 
bisporangiate strobilus or cone. This is especially apparent in 
the angiosperms where the monosporangiate flower usually shows 
vestiges of one or the other set of sporophylls. These vestiges in 
the angiosperm flower are very conclusive, and in deciding whether 
a given structure is primitive or specialized their recognition 
becomes of primary importance. 
The general progression is then about as follows: 
1. Indefinite bands of sporophylls with further growth of the 
axis. 
2. Definite bisporangiate strobili. 
3. Development of a perianth in the Anthophyta. 
4. Reduction of the floral organs to definite cycles and 
numbers. 
5. Extreme modifications in the typical floral organs and also 
in the parts immediately surrounding. 
As often pointed out the evolutionary lines in the flower are 
then : 
1. From spiral to cyclic and to reduced cycles, in the 
monocotyls mostly trimerous, occasionally tetramerous or dimer- 
ous, and' in the dicotyls mostly pentamerous, but occasionally 
tetramerous, trimerous or dimerous. 
2. From pentacyclic to tetracyclic or still fewer sets. 
3. From hypogynous to perigynous and epigynous conditions. 
4. From parts free to parts united, as from apocarpy to 
syncarpy. 
