noun
definition
The leaf of a fern, especially a compound leaf.
definition
Any fern-like leaf or other object resembling a fern leaf.
Examples of fronds in a Sentence
The blanched fronds are also sold in large quantities for the processions of Palm Sunday, and after they have received the blessing of the priest they are regarded throughout Spain as certain defences against lightning.
P. dryopteris, generally known as oakfern, is a very graceful plant with delicate fronds, 6 to 12 in.
If during this process part of the fronds run together, the beauty of the specimen may be restored by dipping the edge into water, so as to float out the part and allow it to subside naturally on the paper.
It is represented in Britain by four species of Lemna, and a still smaller and simpler plant, Wolfa, in which the fronds are only one-twentieth of an inch long and have no roots.
The fronds of some of these Carboniferous ferns are almost identical with those of living species.
P. phegopteris (beechfern) is a graceful species with a black, slender root-stock, from which the pinnate fronds rise on long stalks, generally about 12 in.
From the lower part of a carpel are produced several laterally placed ovules, which become bright red or orange on ripening; the bright fleshy seeds, which in some species are as large as a goose's egg, and the tawny spreading carpels produce a pleasing combination of colour in the midst of the long dark-green fronds, which curve gracefully upwards and outwards from the summit of the columnar stem.
In others again (Woodwardia orientalis, Asplenium bulbiferum), buds are numerously produced on the upper surface of the fronds.
Some species of saxifrage and of ferns also produce buds on their leaves and fronds.
Similarly, the dead fronds fall off,leaving a ragged petiole, which is afterwards separated from the stem by an abscess-layer a short distance above the base.
In Cycas the stem apex, after producing a cluster of carpellary leaves, continues to elongate and produces more budscales, which are afterwards pushed aside as a fresh crown of fronds is developed.
Such ferns as Gymnogrammas, which have their surface covered with golden or silver powder, and certain species of scalysurfaced Cheilanthes and Nothochlaena, as they cannot bear to have their fronds wetted, should never be syringed; but most other ferns may have a moderate sprinkling occasionally (not necessarily daily) and as the season advances sufficient air and light must be admitted.
When found detached these leaves were taken for the fronds of a Fern.
No traces of sori have so far been found on the fronds.
There are various cultivated forms - cristata has the ends of the fronds and the pinnae finely crested, and corymbifera has curiously forked and crested fronds.
The great majority of specimens of fossil fern-like plants are preserved in the form of carbonaceous impressions of fronds, often of remarkable perfection and beauty.
It is, however, probable that a considerable group of true Ferns, allied to Marattiaceae, existed in Palaeozoic times, side by side with simpler forms. In one respect the fronds of many Palaeozoic Ferns and Pteridosperms were peculiar, namely, in the presence on their rachis, and at the base of their pinnae, of anomalous leaflets, often totally different in form and venation from the ordinary pinnules.
Typically Marattiaceous sori, consisting of exannulate sporangia united to form synangia, are frequent, and are almost always found on fronds with the character of Pecopteris, large, repeatedly pinnate leaves, resembling those of Cyatheaceae or some species of Nephrodium.
There is evidence that in many cases these Pecopteroid fronds belonged to arborescent plants, the stems on which they were borne reaching a height of as much as 60 ft.
The genus Asterotheca includes a number of Ferns, chiefly of Coal Measure age, with fronds of the Pecopteris type.
In many fern-like plants of this period the fronds were dimorphic, the fertile leaves or pinnae having a form quite different from that of the vegetative portions.
It is characteristic of Zygopteris and its near allies that two rows of pinnae were borne on each side of the rachis, at least in the fertile fronds.
In 1905 Grand' Eury discovered the seeds of Pecopteris Pluckeneti, an Upper Coal Measure species, attached, in immense numbers, to the fronds, which are but little modified as compared with the ordinary vegetative foliage.
There is reason to believe that other species of Pecopteris and similar genera, (Callipteris and Mariopteris) bore seeds, though the artificial group Pecopterideae probably also includes the fronds of true Marattiaceous Ferns.
Archaeocalamites, Bothrodendron, Archaeopteris, Megalopteris, &c. Among fern-like fronds Diplotmema and Rhacopteris are characteristic. Some of the Lepidodendreae appear to approach Sigillariae in external characters.
Numerous fronds such as Alethopteris Neuropteris, Mariopteris, &c., belonged to Pteridosperms, of which specimens showing structure are frequent in certain beds.
The genus possessed small broadly oval or triangular leaves in addition to the large fronds like that shown in fig.
Among the large number of Mesozoic Ferns there are several species founded on sterile fronds which possess but little interest Filicales, from a botanical standpoint.
As examples of these doubtful forms may be mentioned Thinnfeldia, characteristic of Rhaetic and Lower Jurassic rocks; Dichopteris, represented by some exceptionally fine Jurassic specimens, described by Zigno, from Italy; and Ctenis, a genus chiefly from Jurassic beds, founded on pinnate fronds like those of Zamia and other Cycads, with linear pinnae characterized by anastomosing veins.
The close resemblance between specimens from Jurassic rocks placed in one or other of the genera Thinnfeldia, Dichopteris, Cycadopteris, &c., illustrates the unsatisfactory custom of founding new names on imperfect fronds.
It has been found useful in some cases to examine microscopically the thin film of coal that often covers the pinnae of fossil fronds, in order to determine the form of the epidermal cells which may be preserved in the carbonized cuticle; rectilinear epidermal cell-walls are usually considered characteristic of Cycads, while cells with undulating walls are more likely to belong to Ferns.
Leaving out of account the numerous sterile fronds which cannot be certainly referred to particular families of Ferns, there are several genera which bear evidence in their sori, and to some extent in the form of the leaf, of their relationship to existing types.
Bipinnate sterile fronds of Todites have in some instances been described under the designation Pecopteris whitbiensis.
The dichotomously-branched fronds, of the type represented by several recent species of Gleichenia, e.g.
The numerous species of fronds from Jurassic and Wealden rocks of North America and Europe referred to Thyrsopteris, a recent monotypic genus confined to Juan Fernandez, are in the majority of cases founded on sterile leaves, and of little or no botanical value.
This type is distinguished by its large bipinnate fronds bearing long and narrow pinnae with close-set pinnules, characterized by the anastomosing secondary veins.
Similarly, the genus Sagenopteris, characterized by a habit like that of Marsilia, and represented by fronds consisting of a few spreading broadly oval or narrow segments, with anastomosing veins, borne on the apex of a common petiole, is abundant in rocks ranging from the Rhaetic to the Wealden, but has not so far been satisfactorily placed.
The evidence adduced by Nathorst and some other writers is, however, not convincing; until we find well-preserved sporocarps in connection with vegetative fronds we prefer to keep an open mind as regards the position of Sagenopteris.
In most cases we have only the evidence of sterile fronds, and this is necessarily unsatisfactory; but the occurrence of numerous stems and fertile shoots demonstrates the wealth of Cycadean plants in many parts of the world, more particularly during the Jurassic and Wealden periods.
From Palaeozoic rocks a few fronds have been described, such as Pterophyllum Fayoli, P. Combrayi, Plagiozamites and the leaves of Todites, a genus which may often be recognized by the broad and relatively short bluntly-terminated pinnules.
Sphenozamites, chiefly from French localities, which are referred to 1 fronds, which therg is good reason to refer to the Cycadales in the Cycads because of their similarity to the pinnate fronds of Upper Triassic, Rhaetic, Jurassic and Wealden rocks in India, modern Cycadaceae.
Dorsetshire and in the Inferior Oolite beds of Yorkshire, as well as in Rhaetic strata in Persia and elsewhere; it is characterized by its bipinnate fronds, and may be compared with the recent Australian genus Bowenia - peculiar among living Cycads in having bipinnate fronds.
Another well-known Cycadean genus is Williamsonia, so named by Mr Carruthers in 1870, and now applied to certain pinnate fronds - e.g.
There can be little doubt that the majority of the Cycadean fronds of Jurassic and Wealden age, which are nearly always found detached from the rest of the plant, were borne on stems of the Bennettites type.
Williamson was the first to express the opinion that the Bennettitean flowers known as Williamsonia were borne on the trunks which terminated in a crown of pinnate fronds of the type long known as Zamites gigas; this view was regarded by Saporta and others as incorrect, and the nature of the Bennettitean foliage was left an open question.
Meanwhile, trim the fennel, reserving the fronds.
Both types are a simple pinnate form but the pinnae of the spore producing fronds are very much narrower.
Some will have incredibly dense fronds that are produced almost vertically which may also twist as well.
Thus any incompletely unfurled fronds may be destroyed by the first autumnal frost, whereas mature fronds may escape.
The light arching fronds of ferns are a lovely addition to baskets hung in shadier positions.