me iy y+ - enter 5 : v 
60 ©LASS-BOOK ‘OF BOTANY, 
(Calendula), Tansy* (Tanacetum), Wormwood* (Artemisia), our conimon 
New Zealand species of Cotula ;* also Daisy (Bellis), Aster, Celmisia, aud 
indeed, all daisy-like plants. These range. from trees, as in our larger 
Olearias and. Senecitos, down to moss-like herbs (Abrotanelia), showing 
very retrograde development ; and, while some have ligulate ray-florets, 
other have all the florets tubular. 
‘(6.). In very many—indeed, the majority—of common 
corkposites—e.g., Thistle (Carduus), Groundsel (Senecio), or 
Yo ae Celimisia—the calyx-limb is developed into 
‘@ persistent crown of bristles or hairs, 
termed a pappus, the function of which 
is manifestly to distribute the seeds by the 
action of wind. ‘The form and deyelop- 
iment of this. pappus differ much in dif- 
ferent species. Fon ot Nig 
(c.) In Corn-bottle (Centaurea cyanus) 
the outer florets are not ligulate, but ob- 
liquely tubular. While among most flowers 
with ligulate rays we find the extra develop- 
ment of the corolla almost always accom- 
_ panied with more or less complete abortion 
Pig. 105.+Diso-floret of the stamens, in these outer florets of 
of Celmisia with ,Centaurea this abortion is complete, so 
pappus. ‘that they are perfectly sterile. Their 
ae function is reduced absolutely to that of 
display, as by their means insects are attracted to the smaller 
but neetar-bearing disc-florets. | 
(d.) Examine any species of native Raouli« or of Everlasting 
Blower (wild or cultivated), and make a longitudinal section 
through the flower-head. Notice that all the florets have 
tubular corollas, the outer row usually ?, the rest ¥, and 
that they are almost hidden in the long dense pappus, while 
the conspicuous portion of the head is formed of the hard, 
coloured, involucral bracts. These and. the previously-cited 
cases furnish additional examples of a law of compensation 
with which you must be now tolerably familiar—namely, that 
when in any particular species an organ does not perform the 
functions which may be considered to belong to it, or per 
forms functions usually. done by. some other organ, then 1ts 
proper work is accomplished by some other means. 
The following are additional genera to, those already named in vie 
this composite structure oecurs in a more or less modified form), Tees 
necessary to remember in examining any of these when under es I 
tion that the original form and structure are often-greatly ae ies 
. .Ageratum, Coreopsis, Cynara (Globe Artichoke), Dahlia, ee Vie 
(Edelweiss, &c.), Helianthus (Sunflower and Jerusalem Artichoke), a9 
{French and African Marigolds), and Zinnia. 
= 
‘ ewer inner in 
*In these the outer florets are. not very different from es re 
form, being all tubtilar ; but the latter are 3, Usé former ¢ only: 
