Small. — Pollen-presentation Mechanism in the Compositae. 461 
apical and basal appendages of the stamens are the expression of a tendency 
to economy of pollen, which is limited only by the biological necessity of 
providing sufficient pollen to ensure fertilization, implies that these appen¬ 
dages will show correlative development, and Tables I and II are an 
attempt to analyse the development of these structures throughout the 
order. 
In such tables it is very difficult to assign the correct value to each 
genus, since a small genus may represent a large, almost extinct group, 
while a large genus may be composed of numerous small variations about 
a single type. It is obvious that a higher value should be given to one 
species of the former genus than to one of the latter. Likewise, if the 
genus is large and variable, it is proper that it should receive a proportionate 
value. Since the task of tabulating the characters of 13,000 species is out 
of the question, the genera have been analysed in the following way: If 
a genus shows one type of style or stamen it has been counted 1 ; if it 
shows two types, then each type has been counted \; and if, as in some 
large genera, it shows three types, then each type has been counted -J, so 
that a large and varied genus has the value 1 \ in the tables. It was thought 
inadvisable to give a genus showing two types a value greater than unity in 
order to keep the numbers approximately those of the genera in each tribe. 
Description of Stamens and Styles. 
The types given here are in most cases of a synthetic character, as 
many of the intermediate stages between one definite type and the others 
occur. In all the types of stamens except types 1 and 4 a the apical 
appendage is present. It is a more or less flattened outgrowth and nearly 
always simple in outline, very rarely bifid. In certain types this appendage 
becomes more elongated (types 6 a , 11, 15, and 16), or, as in Sclerolepis 
(Fig. 5), it may become truncate, or it may have the apex inflexed, as in 
the Ambrosinae. Type 1, in which the apical appendage is absent, occurs 
only in the Piquerinae, a sub-tribe of the Eupatorieae; 4 a is a rare type 
which occurs only in Eleuther anther a : it is type 4 without the apical 
appendage. Type 6 a is interesting as occurring in a discoid genus of 
Senecioneae, Culcitium . This type and type 11, which occurs in the 
Mutiseae ( Leuceria ), are to be compared with the elongated apical appen¬ 
dages of types 15 and 16, which are the typical forms for the Cynareae. 
The basal appendages show more variation. They are absent entirely 
from types 1, 2, and 3. In the other types the polliniferous region is shaded 
so that the appendages may be clearly distinguished. Type 4 shows 
a sagittate stamen with very small auricles; types 5 and 6 show these 
auricles enlarged : in the former they are obtuse, in the latter acute. Type 6 b 
occurs very seldom : the auricles here are enlarged. Type 7 is a sagittate 
stamen with the auricles connate ; type 8 shows the beginning of the 
