29 
Notes on the Corolla in the Composite. 
of five-toothed ray florets. I am of opinion, however, that those 
exceptional forms are due to the irregular or abnormal development 
of the posterior lobes rather than to the distinctive process by which 
the truly ligulate corolla is developed. The genus Hieracium has a 
literature of its own, and although Ostenfeld (26) shows that 
polymorphism in this genus is correlated with apogamy, his 
results seem to point to the occurrence of mutations (as well as 
hybridisations) which would be preserved by the prevalent apogamy. 
Kajanus (16) also records a mutation. The occurrence of mutants 
in both the Senecioneae and the Cichorieae is especially interesting 
and the suggestion of the origin of the latter tribe by mutation is 
strengthened. 
Development of the Corolla. 
Floral development in the Compositae is easily observed and 
has been the subject of numerous researches. Payer’s figures (27) 
are not to be surpassed, and it is easy to follow the development of 
the three types of corolla from his illustrations of Heliopsis scabra 
ray and disc florets, Centaurea jacea, Hieracium umbellatum and 
Cichorium Intybus. 
Other authors have merely extended the range of observations 
and included some abnormal forms. In the tubular florets the 
lobes are equal throughout all the stages of development, (Figs. 
25-27). In the bilabiate florets the lobes become differentiated at 
an early stage (Figs. 29, 30); there may be a deep posterior 
indentation, and this, by the subsequent development of the usually 
abortive lobes, would give a pseudo-ligulate corolla, as in the 
Mutisieae (e.g., Ainslicea, Catamixis, Pasaccardoa and Dinoseris) 
and the rare cases in other tribes (e.g., Stokesia spp., Anthemis spp., 
Helenium spp., Calendula spp.). The deep indentations may occur 
on each side of the posterior lip and the development of this lip 
would give the bilabiate forms of the Mutisieae and the abnormal, 
distinctly bilabiate forms in other tribes. The posterior lobes 
usually abort completely and there is practically always an over¬ 
lapping of the edges of the ‘ ligule ’ (Figs. 20, 28) which is not 
shown by Payer. 
The ligulate floret arises in quite a different manner by the 
failure of the tissue connecting one posterior petal to the other to 
develop (Figs. 31-33). From a very early stage there is no doubt 
of the posterior split, and although the corolla tube may, at a later 
stage, elongate a little at the base it is always as different in 
appearance from the pseudo-ligulate rays as it is in development. 
