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James Small. 
to be a distinct movement of a higher type. C' and C e are 
obviously special developments of the general C type. 
In Senecio the C type is the commonest, while allied genera 
such as Arnica, Cineraria and Othonnopsis show the higher types, 
A or B. The Tussilagininae and Vernonieae with a pollen presenta¬ 
tion like that of the Eupatorieae show no irritability, nor does the 
latter tribe. The Cichorieas are distinguished by a peculiar, slow, 
lateral movement of the primitive C type ; this type of movement 
also occurs in Senecio Ligularia, var. speciosa. The C type is very 
active and highly developed in the Calenduleae, notably in 
Dimorphotheca. The Arctotidese combine an irritable style with 
the C type of staminal movement. The Anthemideae and Inuleae 
show an increase in the type A movement, while type C remains 
predominant. Six of the nine sub-tribes in the Inuleae have been 
examined and five show irritability. Type B is shown in a number 
of Cynareae, and this is to be correlated with the occurrence of the 
same type in Buphthalmum salicifolium. Type C' seems to be 
confined to the genus Centaurea, except for the intermediate stage 
shown by Erigeron and Heliopsis (see notes 32 and 34). The 
explosive type, C e , is confined to the Mutisieae. 
Five of the six sub-tribes in the Astereae have been examined 
and all show irritability, mostly of the C type, but with type A 
common and developed to a notable extent in Aster and even 
more so in Erigeron . Three of the five tribes in the Helenieae 
have been examined, and only one (Helenieae) shows irritability 
with certainty. This is noteworthy, and is to be correlated with 
the number of genera in the Heliantheae which show no irritability. 
Seven of the ten sub-tribes in the Heliantheae have been examined, 
and six show irritability. Irritability is scarcely to be 
expected in the dioecious forms of the Ambrosiinae ; the predomin¬ 
ance of the C type in the Verbesiinae and the large proportion of 
the A type in the Melampodiinae and Coreopsidinae are to be noted. 
D. Physiology of Irritability. 
Apart from such statements as that of Bose (3) that the 
stamens in the Compositae are truly sensitive, Cassini’s sugges¬ 
tion (6) of the death of the filaments as the cause, that of Ker (30) 
that the movement of the style in Arctotis is due merely to 
elasticity and Meehan’s similar explanation (41) of the movement 
of the stamens in Helianthus, with the contradictions by Brown (4) 
and Gray (13-14), considerable progress has been made with the 
study of the general phenomena of irritability. Smith (51) 
