ANGIOSPERMS. 
549 
into existence at all, if the hypothesis of the suppression of the part is confirmed 
by a comparison of the relationships of number and position in nearly-allied plants. 
The hypothesis of an abortion of this kind was, however, for the first time placed 
on a firm basis by the theory of descent. 
The number of stamens in a flower is only rarely so few as one or two ; like 
the perianth-leaves they are usually numerous, and they are then arranged in the 
form of rosettes, either spirally or in whorls. If the arrangement of the perianth- 
leaves is spiral, that of the stamens is usually the same, and the number of the 
latter is then very commonly large and indefinite, as in Nymphcea, Magnolia, Ranun- 
culus, Helleborus, &c. ; but in this case they are sometimes also few in number and 
definite. 
Much more often, however, the stamens are arranged in one or more whorls, 
those in one whorl being then usually equal in number and alternate with those in 
Fig. 373.— Various stages of development of the flower of Lamiimt alhum; I, II, III very young buds 
seen from above ; in / the rudiments of the sepals s are formed, in // those of the petals in /// those of the 
stamens st and of the carpels c; horizontal section of an older bud, j tube of the gamosepalous calyx, / that 
of the gamopetalous corolla ; a anthers, n stigmas ; V upper lip of the corolla with the epipetalous stamens ; 
VI entire mature flower seen from the side. 
the other whorls, and with the perianth-leaves [symmetrical flowers of English text- 
books]. There are, however, numerous deviations from this rule [unsymmetrical 
flowers of English text-books] occasioned frequently by the abortion of particular 
members or of whole whorls, or by their multipHcation, or by the superposition of 
consecutive whorls; and not unfrequently in the place of a single stamen two or 
even m.ore will arise side by side {dedoublemenl). These phenomena, which are 
often difficult to make out, are nevertheless of great value in the determination of 
natural affinities, and will be still further examined in the sequel. 
Development of the Pollen and of the Anther-wall^. The description given in 
this place will apply only to the ordinary cases in which the pollen is formed in 
^ Nägeli, Zur Entwickelungsgeschichte des Pollens, Zurich, 1842. — Hofmeister, Neue Beiträge 
zur Kenntniss der Embryobildung der Phanerogamen, II. Monocotyledonen. — Warming, Unters, üb. 
pollenbildende Phyllome und Caulome, in Hanstein's Bot. Abhdl. Bd. II. 1873. — [Goebel, Beit. z. 
Entwickgesch. d. Sporangien, Bot. Zeit. 1881.] 
