73 
As Bessey* says they are ootianlid accepted inniples as 
applied to flowering plants, at any rate with those who believe 
that petaliferous plants preceded apetalous ones and that the 
latter have arisen through reduction. 
*GENERAL PRINCIPLES ADOPTED FOR THE CLASSIFICATION 
F FLOWERING PLANTS. 
Other things being equal, it may be stated that :— 
(1) Evolution is both upwards and downwards, the latter 
involving degradation and degeneration ; examples : 
—the apetalous state of many flowers ; unisexuality 
in flowering plants. 
(2) Evolution does not necessarily involve all organs of the 
plant at the same time, and one organ or set of 
organs may be advancing whilst another set is 
stationary or retrograding. 
(3) Evolution has generally been consistent, and when a 
particular progression or retrogression has set in it 
is persisted in to the end of the phylum ; examples :— 
the strong tendency to zygomorphy of the corolla 
coupled with the reduction in the number of stamens 
in the hypogynous M etachlamydeae ; the great 
tendency to perigyny and epigyny in the Archi- 
chlamydeae and Metachlamydeae, as exhibited in the 
families Umbelliferae and Rubiaceae respectively. 
Relating to the general habit of plants. 
(4) In certain groups, trees and shrubs are probably more 
primitive than herbs; examples, Mimosaceae an nd 
Caesalpiniaceae (trees and shrubs) as compared with 
the pear family Papilionaceae (Fabaceae) (mostly 
herbaceo 
(5) Trees and aie are older than climbers, the latter 
— bit having been acquired through particular 
nvironmen 
(6) Derciiszals are older than biennials, and from them 
annuals have been derived ; note the extraordinarily 
few annuals in the primitive family Ranunculaceae ; 
the great number in the Cruciferae. 
(7) Aquatic eee oe are as a rule more recent than 
rrestrial (at any rate in the members of the same 
family or genus), and the same may be said of 
epiphytes, saprophytes, and parasites. 
Relating to the general structure of flowering plants. 
(8) Plants with collateral vascular bundles arranged in a 
bare (Dicotyledons) are more primitive in origin 
* The reader is referred here to a second essay by Bessey, ‘ Pte da 
genetic Tatononiy.” published in the Annals of the Soper ail’ Ba 
Garden, vol. 2: 112. The present writer cannot accept all sess 
ganeenlainiind: but his Pip ob are given above together with a few 
additional observations 
