. Plants; a text-book of botany. Botany. 222 PLANT STRUCTnEES " without ; It is not always possible to tell whether a flower is apetalous—that is, whether it has lost a floral set which it once had—or is simply one whose perianth has not yet differentiated, in which case it would be a "primi- tive ; The line of evolution, therefore, extends from flowers without floral leaves, or naked flowers, to those with a dis- tinctly difl^erentiated calyx and corolla. 121. Spiral to cyclic flowers.—In the simplest flowers the sporophylls and floral leaves (if any) are distr
. Plants; a text-book of botany. Botany. 222 PLANT STRUCTnEES " without ; It is not always possible to tell whether a flower is apetalous—that is, whether it has lost a floral set which it once had—or is simply one whose perianth has not yet differentiated, in which case it would be a "primi- tive ; The line of evolution, therefore, extends from flowers without floral leaves, or naked flowers, to those with a dis- tinctly difl^erentiated calyx and corolla. 121. Spiral to cyclic flowers.—In the simplest flowers the sporophylls and floral leaves (if any) are distributed about an elongated axis in a spiral, like a succession of leaves. That part of the axis which bears the floral organs is for convenience called the receptacle (Fig. 202). As the recep-. Fig. 203. A buttercup {Eanvncithis): a, complete flower, showing sepals, petals, sta- meiiK, and head of numerous carpels on a large receptacle; 6, section showing relation of parts; a hypogynous, polypetalous, apocarpous, actinomorphic flower. —After Baillon. tacle is elongated and capable of continued growth, an in- definite number of each floral organ may appear, especially of the sporophylls. With the spiral arrangement, there- fore, there is no definiteness in the number of floral organs ; there may be one or very many floral leaves, or stamens, or carpels. The spiral arrangement and indefinite numbers are features of the ordinary strobilus, and therefore such flowers are regarded as more primitive than the others. In higher forms the receptacle becomes shorter, the spiral more closely coiled, until finally the sets of organs. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Coulter, John Merle, 1851-1928. New York, D. Appleton and company
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