290 
H. F. Wernham. 
FLORAL EVOLUTION : WITH PARTICULAR REFERENCE 
TO THE SYMPETALOUS DICOTYLEDONS. 
By H. F. Wkrnham. 
VIII. Infers: Part II. Campanulat^;. 
| )HE group with which we are about to deal includes those 
floral forms which are generally regarded as the most highly 
organized in existence, namely the Composite. Their success 
under the judgment of Natural Selection is evidenced by the 
enormous number of species (over 11,000) which find a place in 
this very natural family; and this success reflects the complete 
realization of all general evolutionary tendencies in combination. 
For the rest, Campanulatae consists of the rather heterogeneous 
Campanulaceae, with about 1,000 species ; of Cucurbitaceae, with 
somewhat doubtful affinity; and of three other families with 
relatively few and highly specialized species. 
The large majority of the Campanulatae are herbaceous; 
arboreal or shrubby forms are rare among Campanulaceae, and 
rarer still among Compositae ; and this is in keeping with the great 
degree of general advance which these groups have attained. 
There is no extensive arboreal group which stands to Campanu¬ 
latae in the same relation, say, as Verbenaceae to Diovulatae. 
The fundamental tendency of the Campanulatae is the approxi¬ 
mation, and ultimate syngenesis, of the anthers; and this tendency 
is in obvious relation to pollination. The mechanism 111 question, 
often referred to as the “ pollen-presentation” mechanism,is familiar 
to most elementary students. The linear anthers dehisce introrsely, 
and so discharge their pollen into the interior of the tube formed by 
their partial or complete union. The young style (the flower being 
protandrous) is clavate, the stigmas being united until the exserted 
style is fully grown, and, in the course of its growth it forces its way 
through the anther-tube, sweeping the pollen gradually before it out 
of the mouth of the tube ; in typical cases the style is provided with 
a brush of hairs to facilitate this sweeping process. When the 
elongation of the style is completed, it projects beyond the rest of 
the flower; and after a time the stigmas mature and separate, and 
present their receptive (ventral) surfaces to insect-visitors, inviting 
them to leave pollen collected from other flowers in the manner 
