Monoecious, and bearing their male flowers in catkins, they are readily distinguished from the rest of the catkin-bearing trees by their peculiar fruit, an acorn or nut, enclosed at the base in a woody cup, formed by the consolidation of numerous involucral bracts developed beneath the fertile flower, simultaneously with a cup-like expansion of the thalamus, to which the bracteal scales are more or less adherent.
The catkins appear soon after the young leaves, usually in England towards the end of May; the acorns, oblong in form, are in shallow cups with short, scarcely projecting scales; the fruit is shed the first autumn, often before the foliage changes.
As in all poplars, the catkins expand in early spring, long before the leaves unfold; the ovaries bear four linear stigma lobes; the capsules ripen in May.
In diameter, and with the shoots or young branches more or less angular; the glossy deltoid leaves are sharply pointed, somewhat cordate at the base, and with flattened petioles; the fertile catkins ripen about the middle of June, when their opening capsules discharge the cottony seeds which have given the tree its common western name; in New England it is sometimes called the "river poplar."
The male catkins are about 12 in.
The leaves of the cypresses are scale-like, overlapping and generally in four rows; the female catkins are roundish, and fewer than the male; the cones consist of from six to ten peltate woody scales, which end in a curved point, and open when the seeds are ripe; the seeds are numerous and winged.
The flowers are unisexual and monoecious, the numerous males borne in thick catkins proceeding from the side of last year's shoot.
Its catkins are collected in England in celebration of Palm Sunday, the bright-coloured flowers being available in early spring when other decorations of the kind are scarce.
Both bear their round or ovoid male catkins at the ends of the slender terminal branchlets; the ovoid cones, either terminal or on short lateral twigs, have thick woody scales dilated at the extremity, with a broad disk depressed in the centre and usually furnished with a short spine; at the base of the scales are from three to seven ovules, which become reversed or partially so by compression, ripening into small angular seed with a narrow wing-like expansion.
At the much Sequoia sempervirens - a, Branch with green cones and male catkins; b, Section or cone; c, Scale of cone.
The male catkins are small, solitary, and are borne at the ends of the twigs; the cones are from 12 to 3 in.
They are as a rule of a very hardy character, thriving best in northern latitudes - the trees having round, slender branches, and serrate, deciduous leaves, with barren and fertile catkins on the same tree, and winged fruits, the so-called seeds.
The male and female flowers are borne on separate catkins in April and May.
The yellow stamen-bearing flowers are in sessile, nearly spherical catkins; the fertile ones vary in colour, from red or purple to greenish-white, in different varieties; the erect cones, which remain long on the branches, are above an inch in length and oblong-ovate in shape, with reddish-brown scales somewhat waved on the edges, the lower bracts usually rather longer than the scales.
The flowers, which appear in March and April, are borne on pendulous hairy catkins, 2 -3 in.
Long; male and female catkins are, as in the other species of the genus, on distinct trees.
The numerous male catkins are generally arranged in dense whorls around the bases of the young shoots; the anther-scales, surmounted by a crest-like appendage, shed their abundant pollen by longitudinal slits; the two ovules at the base of the inner side of each fertile cone-scale develop into a pair of winged seeds, which drop from the opening scales when mature - as in the allied genera.
The leaves are rather short, curved, and often twisted; the male catkins, in dense cylindrical whorls, fill the air of the forest with their sulphur-like pollen in May or June, and fecundate the purple female flowers, which, at first sessile and erect, then become recurved on a lengthening stalk; the ovate cones, about the length of the leaves, do not reach maturity until the autumn of the following year, and the seeds are seldom scattered until the third spring; the cone-scales terminate in a pyramidal FIG.
Broad; the male catkins are of a bluish tint; the cones ripen in the autumn of the second year.
The flowers, which appear in early summer, are in pendulous, slender yellowish catkins, which bear a number of staminate flowers with a few pistillate flowers at the base.
The stout cylindrical male catkins are pendulous, reddish in colour and 2 to 4 in.
The plants are trees or shrubs with simple leaves alternately arranged and small unisexual flowers generally arranged in catkins and pollinated by wind-agency.
Female flowers arranged, two to three together on scale-like structures formed by the union of bracts, in catkins; ovary two-celled; fruit small, flattened, protected between the ripened scales of the catkin.
The so-called catkins of the birch are, in reality, spikes of contracted dichasial cymes.
The inflorescence is usually a spike bearing lateral cones or catkins, arranged sometimes distichously, sometimes in a spiral order.
The organ figured is one of the catkins (about a centimetre in length) which were borne laterally on the spike.
The female inflorescences vary considerably in organization; in some species the axis of the spike bears solitary ovules, each accompanied by a few bracts, while in others the lateral appendages are catkins, each containing from two to several ovules.
The amber yields such things as fallen flowers, perfect catkins of oak, pollen grains and fungi.