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CONSECUTIVE LEAF-FORMS 15 
seen in A. roscidus ; <A. divaricatus fontinalis and A. viridis are 
similar. 
N?, Cauline stage, the radical tuft sending up an erect leafy 
stem, usually without passing through the last two stages, and 
often without retaining its radical leaves, but developing three 
principal shapes below the branches, the lower, middle and upper 
caulines already described, these changing gradually into each 
other, but their particular form being characteristic of the particular 
species. But instead of taking this normal course of development, 
N?, the plant may enter into any of the following seven stages 
which I enumerate as accidental or less usual. 
A’. Intercalary stage, when one or more little leaves are inter- 
calated into the series, with much larger leaves above and below. 
Occasional in Biotian asters, especially in A. Schreberi; the appear- 
ance seeming like the exhibition by the plant of a rhythmic ebb 
and flow in its energy ; possibly due to a short period of diminished 
nutrition. 
A‘. Arrested stage, when the gradually diminishing normal 
series of cauline leaves meets sudden arrest from which it never 
recovers, a succession of little leaves now continuing into the 
inflorescence, making the inflorescence seem raised on a long 
peduncle. Such an arrest is particularly apt to occur in late-devel- 
oping or feebly nourished plants. It is frequent in the allies of A. 
cordifolius, of A. macrophyllus and A. Schrebert. In a few species, 
as A. multiformis, there is a marked tendency to adopt this habit of 
growth. I doubt, however, if there is any case in which it has 
become persistent enough to form by itself a valid specific char- 
acter, except in A. biformis. 
A*. Sprout-form ; due to development of a lateral bud near the 
ground, either on the base of a vertical stem or on the rootstock 
near it; occasioned sometimes by excess of vigor in the plant as a 
whole, sometimes by the clogging of the main stem with age. 
Sprout-forms usually have the leaves somewhat different from the 
type, larger or smaller or very much narrowed or otherwise peculiar 
in shape. All species are liable to them, as also to the next, and 
their characters must be separately determined for each species. 
A*. Ramifolial or branch-form, when after suppression of the 
main stem, one or more branches rise to replace it; often due to 
