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ALTERNATION OF LEAVES, ° 61 
100. It has been shown that when two leaves become 
opposite on a stem, the pair of leayes above and below 
is usually placed alternate with them and so on; and, 
when three or four leaves form a whorl, the next whorl 
above or below alternates also with it. If the calyx 
be considered to be a whorl of leaves, and the petals 
another, and the stamens, when few in number, say 
three, four, or five, another; and the ovaries another; 
these different whorls should be found to follow the 
same rule.as whorls of leaves do on the stem below: 
and such is the fact, for example, the flower of the 
Strawberry (pl. 20. f. 7.) has five sepals, and outside 
these sepals (s.) are five bracts (0.), which will be found 
to be placed alternate to the sepals. The same 
arrangement exists with regard to the petals (f. 6. p.), 
which alternate with the sepals; thus we have already 
three whorls of organs which alternate with each other, 
the bracts with the sepals, and these with the petals. 
101. The same rule holds good in the flower of the 
Flax, in which there are no bracts, but the sepals 
alternate with the petals; f. 8. is a cross section of 
the flower, showing how the different parts are placed 
with regard to each other; s. s. are the sepals; p. p. 
the petals; there are besides five stamens (st.), which 
may be seen to alternate with the petals, but to be 
placed opposite to the sepals, and in the centre may be 
seen the ovary cut across, and consisting of five carpels 
(¢.), each containing two ovules; and these five carpels 
are placed alternate to the five stamens. 
102. In the flower of the Rue (f. 11.) we find five 
sepals, (sometimes only four), five petals, and ten 
