SYSTELAB MIDTERMS I

• Ferns are seedless vascular plants, which are often found in moist and shaded places.
• Like the other vascular plants, ferns exhibit a definite alternation of generation, with the sporophyte the dominant generation.
• In ferns, the gametophyte is reduced but independent of the sporophyte.
• Ferns produce only spores usually in clusters of stalked sporangia called sori.
• Ferns are mostly homosporous.
• The gametophyte of ferns germinates outside of the microspores (exosporic).
• The fern sporophyte has an underground rhizome, which could be compact and stubby or elongated reaching considerable length.
• Adventitious roots, usually fibrous in nature, arise

  from the rhizome along with the leaves, which are the most prominent part of the fern plant.
• Fern leaves vary greatly in size and form and are the distinctive organs of this group of plants. It is called a megaphyll because of the presence of a complex vascular system or veins.
• Fern leaves are usually called fronds, and when young are rolled into tight spirals called the crozier or fiddlehead.
• Gradually, the crozier unwinds to form the expanded portion of the leaf during its development called circinate vernation.
• Fern leaves may be simple. A mature frond is attached to the rhizome by a stalk called the stipe.
• Ferns leaves are often compound consisting of a dissected blade wherein each leaflet is called a pinna and is described as pinnate.
• If the pinna is further dissected, each leaflet is called a pinnule and the leaf is described as bipinnate.
• Each pinna is attached to a central axis called the rachis.
• Each pinna will show a certain venation pattern.
• The central vein is called a midrib. The latter veins do not interlock but pass directly to the leaf margin. This is referred to as free venation.
• Unlike the lower vascular plants which bear the sporangia in strobili, spores of ferns are borne in sporangia which ordinarily develop on the lower surface of the leaves.
• The distribution of the sporangia varies with the genera and species. Sporangia may be distributed throughout the entire lower surface of the leaf, grouped together in sori and grow in definite relationship with veins or grow along margins of the leaf.
• An umbrella-like structure, the indusium, may be present when sporangia are grouped together to form a sorus.
• The indusium serves as protection for the young and developing sporangia.
• Some ferns having marginal sporangia form a false indusium by curling the edges of the leaf.
• The ferns are classified into three orders: Filicales (true ferns), Ophioglossales (ophioglossum group) and the Marattiales (Marattia group).
• Filicales produce sporangia that are one-cell thick and stalked. Ophioglossales and Marattiales produce scattered or fused sporangia.
• Flowering plants or the angiosperms are the most abundant, diverse and widespread of all present-day land plants.
• Angiosperms owe their success to the evolution of structural and physiological features that enabled them to establish in a wide variety of habitat. Of the various structural parts evolved, the flower and fruit are considered more significant.
• The flower consists of four whorls of floral parts: the sepal, petals, stamen and pistil.
• The outermost whorl of sepals, collectively termed calyx, are usually green and primarily to protect the flower bud.
• The petals, collectively called the corolla, usually exhibit various colors and play a major role in pollination by attracting agents of pollination such as insects.
• The stamens and the pistil are the fertile parts of the flower.
• The stamen produces the pollen grain and the centrally located pistil, which consists of the carpels, contains the ovule and ultimate the embryo sac.
• Aside from the development of the flower, other features that distinguish the angiosperms from the other spermatophytes are; a) enclosure of the seed within the ovary, which is part of the pistil, and b) the development of the endosperm, a nutritive tissue for the developing embryo, as a result of double fertilization.
• Other features that distinguish angiosperms include the transformation of the ovary into fruit and the presence of well develop vessels in the xylem tissue and sieve tube elements in the phloem tissue.
• Of all the characteristics of flowering plants, the flower and the fruit are the least affected by changes in the environment, hence theae are considered “conservative” structures.
• These features (flowers and fruits) are therefore of great value in both plant identification and in tracing evolutionary relationships. Much consideration is therefore placed in the flower for further classification of the angiosperms.
• Angiosperms show great variation in form. They vary from very simple stemless, free-floating forms to a whole series of herbaceous types to shrubs and trees.
• The angiosperms are divided into two classes; Class Magnoliopsida or Dicotyledonae (the dicots) and Class Liliopsida or Monocotyledonea (the monocots).
• The dicots are primarily characterized by having two cotyledons, rarely one, three or four.
• The floral parts of dicots like the petals are normally in sets of 4’s or 5’s.
• The root system in dicots is either primary (with primary taproot) or adventitious.