Origin and Development of the Compositce. 87 
development of the hairs on the fruit into the pappus mechanism 
may be a fortunate accident or an epharmonic variation; there is 
no clear evidence on this point at present. Thus we arrive at a 
plant with all the essential characters of a Senecio. 
It must be noted that we started with a Siphocampylus with 
characters and tendencies which are known to be present in the 
genus, and we have appealed only to those orthogenetic lines or 
critical tendencies and to the direct influence of the external con¬ 
ditions to effect the change from a species of the Lobelioideae to 
a species of the primitive genus of the Compositae. The orthogene¬ 
tic saltation in almost every detail involves the loss or suppression 
of a character and presumably of a factor, This is in accordance 
with Bateson’s view of mutation (35). The progressive develop¬ 
ment of appendages to the stamens, may also be due to loss, if the 
view given in Chap. II of the origin of the appendages by the 
sterilisation of potentially sporogenous tissue is correct. The 
steps in the change from one genus to the other are natural and 
occur in related forms in the same region. Indeed, there is a 
distinct possibility that even at the present time a close examina¬ 
tion of the variation of the species of the Lobelioideae and Senecio 
in the critical region from the edge of the Matto Grosso to the 
puna of the Sierra would show the actual occurrence of forms such 
as have been suggested. These forms have already been observed 
in closely related genera in that particular region. 
In any case, from the strictly scientific point of view a close 
affinity can be traced between the Lobelioideae of the Andes and 
Senecio. So close is the affinity that we may be permitted to 
suggest a doubt as to the truth, in the case of the Composite, of 
the dictum of De Vries which is quoted by Horne (28) that “ the 
great lines of evolution of whole families and even of genera. 
obviously lie outside the limits of experimental observation.” 
The first three questions given in Section A of this chapter 
have been answered. The fourth—“ at what geological time did the 
Compositae arise ?”—is considered in Section A of the following 
chapter. 
BIBLIOGRAPHY XI. 
1. Babcock, E. B. Walnut mutant investigations. Proc. national Acad. 
Sci., Vol. I, p. 535, 1915. 
2. Bancroft, N. A Review of Literature concerning the Evolution of 
Monocotyledons. New Phytologist, Vol, XIII, (Rep. 
No. 9), 1914. 
3. Bartlett, H. H. Mass Mutation in Oenothcva pvaticola. Bot. Gaa., Vol. 
LX, p. 425, 1915. 
4. „ „ Mutation en masse. Amer. Nat., Vol. XXXIX, p. 129, 
1915. 
