Origin and Development of the Composite ?. 81 
Another point to be noticed is the incipient basal appendages 
in Pratia tnacrodon (Fig. 52), which are specially interesting as 
they occur where the filaments are free, a rather unusual condition 
in the Lobelioidese, where the filaments are usually fused to form 
a tube. 
The frequent occurrence of apical appendages and the rare 
occurrence of basal appendages to the anthers in the Lobelioideae 
compare well with the prevalence in the Composite of the former 
and the gradual development of the latter from a type in which 
they are absent. That the biological significance of the apical 
appendages is the same as in the Compositae is obvious when the 
more or less horizontal position of the anther tube is noted together 
with the position of the appendages (cp. Figs. 46, 47, 50 and 51). In 
the cases such as Lysipomia muscoides, where all the anthers are 
equally appendaged, the anther tube is usually, if not always, erect. 
Irritability of the style or stamens has not yet been observed 
with certainty (cp. 111,49, p. 267), but in Lobelia thapsoides and 
L. cardinalis a very slight touch on the filaments or anther tube, 
is sufficient to produce the presentation of a small quantity of 
pollen. It has not yet been ascertained whether this is due 
to a contraction of the filaments, which are united into a tube, or 
to the delicate adjustment of the style with its sweeping hairs 
inside the anther tube. Observations on this point in the natural 
habitats of the species would be of interest (cp. Torenia, Chap. Ill, 
B) . 
Corolla. Although typically bilabiate or irregular, the corolla 
is not infrequently almost or quite radially symmetric, as in some 
species of Centropogon, Siphocampylus (Figs 53-55), Dialypetalum, 
Laurentia, Hypsela, Lysipomia, Rhizocephalum, Isotoma, Brighamia, 
and Downingia. Indeed, there is a general tendency for the corolla 
to become more or less radially symmetric whenever the flowers 
become crowded or reduced in size (cp. Fig. 54 and Dialypetalum). 
The colours of the corolla are usually of the higher types, blue 
red or purple, but orange and yellow occur in some species of 
Siphocampylus, Centropogon, Heterotoma and Downingia. 
Calyx. The progressive reduction of the free lobes of the calyx 
from more or less foliose structures to mere undulations at the top 
of the receptacle is illustrated in the genus Siphocampylus (Figs. 53. 
55). The other genera show even more foliaceous sepals as a 
rule, but reduction is comparatively common ; the extreme condition, 
as in Fig. 55, is reached in several genera. 
