166 BOTANICAL GAZETTE | SEPTEMBER 
in the absence of a perianth, the ‘“gynzecium, placentation, 
ovules, fruit and seeds agreeing completely,” as pointed out by 
Niedenzu* in his discussion of the relationship of Tamaricacee. 
If we were to suggest a natural classification of the dicotyle- 
dons based upon the morphology of the sterile flower leaves alone, 
we should group together first those plants with all their flower 
leaves free from one another ; this would constitute our primitive 
group. In another place we should bring together all those in 
which the sterile and spore-bearing flower leaves have undergone 
the greatest fusion; this would constitute our highest group. 
Between these we should have to arrange the intermediate con- 
ditions. Then remembering that the perianth readily becomes 
much reduced we should have to give such place and position to 
each apetalous plant as its structure otherwise demanded. 
Pollen leaves (microsporophylls, stamens).—The normal 
position of these is between the sterile and the ovule leaves. 
In many cases they are quite separate from one another and 
from the other leaves of the flower, but in many other cases they 
are united to one another, or to the leaves below or above. 
Numerically the pollen leaves show great diversity. This is 
correlated with the greater or less amount of pollen required to 
insure the production of seeds in the different species. In gen- 
eral, no organs of the flower exhibit so little constancy in struc- 
ture, dimensions, number, or position as the pollen leaves, and 
yet within narrow limits these inconstant organs often present a 
surprising conformity to a single type. They serve well, there- 
fore, to define the smaller groups, but have little value as indi- 
cating broader relationships. 
Ovule leaves (macrosporophylls, carpels).— These occupy 
the highest portion of the strobilus, and are normally separate 
organs, unconnected with one another or with other organs. In 
buttercups (Ranunculacez), potentillas (Rosacee), and water- 
plantains (Alismaceze) the carpels are many and separate, while 
in pinks (Caryophyllacez), saxifrages (Saxifragacee), and lilies 
(Liliacez) they are more or less united with one another, thus 
™ ENGLER and PRANTL. Die Natiirlichen Pflanzenfamilien g°s 201. 
