Flowers 
is the number of ray florets in the heads of various 
composites, It has been found that the American Aster 
prenanthoides varies in this respect according to the 
season. Early in the year, the average number of ray 
florets is small ; they reach a maximum in summer, and 
then gradually decrease again. But towards the end 
of the season there is often a slight increase in the 
average number of ray florets.!® 
So that there really is a variation in flowers when 
tested by statistics, which is a very important point. 
In a systematic account of the genus Erigeron, it was 
tried to trace the history of the various changes, In 
Linosyris, for instance, (1) all the flowers in the head are 
similar, (2) In the next stage some of the outer florets 
have lost their stamens. (3) Next these outer florets 
became threadlike and altered in shape (as e.g. in Conyza), 
by the .petal-tube contracting on the style. (4) Some 
of these outer florets enlarged their petals and became 
ray florets (Trimorpha). (5) These attractive florets 
became sterile, and the inner threadlike florets became 
female only.” 
For these changes to have happened, one would like 
to know how, for instance, the flowers in the second 
stage lost their stamens, 
But when a kind of savoury (Satureja hortensis) is 
cultivated in particularly poor soil, it shows a tendency 
to suppress its stamens. 
As a rule, in this plant 79 per cent. of the flowers 
possess both stamens and carpels, but in very poor soil 
this may sink to 17 per cent. or even 13 per cent. 
Also, at the end of the season, almost all the flowers 
have no stamens at all.° 
So such changes as those of Erigeron are not neces- 
sarily inexplicable, they may be directly connected with 
the climatic conditions. 
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