Origin and Development of the Composite. 
21 
observations on the causes of doubling in various capitulate species 
(55-56a). In the Compositae he mentions a doubling of Matricaria 
inodora as due to Peronospora Radii (56), and in Beilis perennis as 
due to Eriophyces sp. (56a). 
More Or less closely allied to the phenomenon of doubling is 
the number of ray florets but as this and the number of involucral 
bracts and receptacular paleae seem to be expressions of the relation 
of phyllotaxis to mechanical laws (see Church, 18, Fig. 46, etc.) the 
whole matter will be discussed latter in a chapter on phyllotaxis. 
B. Variation in Form of the Corolla. 
The main thesis of this section is that the ordinary ray floret 
of the tribes other than the Cichorieae has really a bilabiate 
structure, the inner lip being aborted as a rule but frequently more 
or less developed. It is, therefore, considered advisable to restrict 
the use of the term ligulate to the five-toothed, properly strap-shaped 
corolla of the Cichorieas. The fundamental type, as is well shown 
by Uexkiill-Gyllenband (Fig. 4, Chap. II), is the tubular corolla with 
a campanulate upper region and five equal lobes. In addition to 
these three types there is a very narrow, tubular form, Fig. 10, A, 
which is described as filiform. 
The Ligulate Type, 
As will be shown later (Section C) the ligulate corolla is 
easily derived directly from the tubular type by a simple splitting or 
rather by the failure of the connecting tissue to develop between 
the two posterior petals. The extreme uniformity of this character 
in the Cichorieae confirms the conclusion from the uniformity of the 
pollen-presentation mechanism that the Cichorieae are monophyletic. 
The origin has been suggested to be mutational by the writer (77), 
who also suggested a recent derivation from the Senecioneae and 
gave as confirmatory evidence of the Senecioneal origin the 
occurrence of a type of pollen grain in Senecio (Fig. 9, 23) which 
is intermediate between the characteristic type of the Tubuliflorae, 
(Fig. 9, 22), and that of the Cichorieae as figured by Beer (Fig. 9, 24). 
The origin of the Cichorieae by mutation involves only two 
marked changes, the development of the ligulate corolla and of 
laticiferous vessels. The problem presented by the latter change 
is being investigated and as a first step the latex has been shown to 
be translocated after the manner of carbohydrates (74). The 
occurrence of transitions from the ordinary mucilage sacs to 
laticiferous vessels and the development of laticiferous tissue of 
