164 BOTANICAL GAZETTE [SEPTEMBER 
of the families, and so too are the opposite leaves of the verbenas 
(Verbenacee), mints (Labiate), honeysuckles (Caprifoliacez), 
and madderworts (Rubiacee). 
Flower leaves——The reproductive strobilus of angiosperms 
consists of a stem upon which are developed spore-bearing and 
sterile leaves. Whether the sterile leaves were originally derived 
from the spore-bearing ones by a process of sterilization, as sug- 
gested by Bower,? need not be discussed here, since such sterili- 
zation, if it ever occurred, must have taken place long before the 
ancestors of the angiosperms crossed the line which separates 
the Pteridophyta from the Spermatophyta. We have here to 
deal with the reproductive strobilus in the form of the flower, in 
which the sterile leaves are well set off from those which bear 
spores. : 
In the simpler cases the sterile leaves (perianth) are separate 
from one another, and this doubtless represents their primitive 
structure. In other cases the flower leaves have fused more or 
less in their growth, this doubtless being a structure derived from 
the simple primitive condition referred to above. In many 
flowers the perianth leaves show no differentiation from one 
another, while in others they are very unlike. In this matter it 
is reasonable to suppose that the primitive flower leaves were at 
least approximately alike in form and dimensions, and _ that 
unlikeness in these particulars arose as a modification of the 
primitive structure. Again we find that in many flowers the 
sterile leaves are in no way connected with the spore-bearing 
leaves, the former being attached ata distinctly lower level upon 
the stem. In other cases, however, there is more or less union 
between the sterile and spore-bearing leaves, in extreme cases 
amounting to complete fusion. Here again it is not hard to 
recognize in united and fused leaves a structure derived from the 
more primitive free leaves. This union of parts may receive the 
general designation of symphysts.*° 
Some flowers have a scanty perianth (apetalous ) and others, 
9 A theory of the strobiius in archegoniate plants. Ann. Bot. 8: 343. 1894- 
*° Greek ovugveis, a growing together, natural joifing. 
