Exercise 5 - Fern Allies and True Ferns

• The existence of vascular tissues paved the way for plants to survive farther away from the water source such as fern-allies (Lycopodiota) and ferns (Euphyllophyta).
• Phylum Lycopodiota

  This group contains leaves that are called as lycophylls, which essentially synonymous with “microphyll” but are specifically associated with lycopods.
• Lycophylls are leaves with single, unbranched (very rarely branched) vein that lacks a gap in the vasculature of the stem.
• Lycopods are also observed to possess dichopodial roots wherein the root apical meristem may branch into two roots and that no other lateral roots develop.
• Phylum Lycopodiota

  Class Lycopodiopsida

  Family Lycopodiaceae (club mosses)

  • Species in this family possess evergreen lycophylls with stems that elongate and branch dichotomously. The lycophylls often densely cover the stem can bear strobilus which consists of sporangia-bearing structures.

  Common examples: Lycopodium sp. and Huperzia sp.
• Phylum Lycopodiota

  Class Isoetopsida

  This Class has two Families: Selaginellaceae and Isoetaceae.

  * Organisms under this class are distinct for the presence of leaf ligules (named from Latin ligula strap, variant of lingula, from lingua tongue) which are thin, membranous outgrowth from the base of the blade that looks like a strap or tongue.
• Class Isoetopsida

  Members of this class are heterosporous which means they bear two kinds of sporangia:

  • a) Megasporangia: sporangia that produce megaspores which give rise to female gametophytes when they germinate, and
  • b) Microsporangia: sporangia that produce microspores that give rise to male gametophytes
• Class Isoetopsida

  Family Isoetaceae (Quillwort family) - There is only one genus which is Isoetes. Distinct parts of the members of this family include:

  • Velum: a membrane covering another structure, and
  • Trabecula: a strand of sterile tissue dividing the cavity in a sporangium
• Class Isoetopsida

  Family Selaginellaceae (Spike-Moss family) - a mosslike plant + ella, this family contains one genus, Selaginella. The species in this family are distinct as their lycophylls can be isomorphic or dimorphic (state of having two different kinds of leaves).
• Phylum Euphyllophyta

  This Phylum can be generally split into two groups as follows:

  • a.) monilophytes – those that bear spores such as ferns, in the broad sense, with the name originating from the Latin word monilo, necklace or string of beads + Gr. phyt, plant) with four major lineages: Equisetopsida (horsetails), Psilotopsida (whisk ferns and ophio glossoid ferns), Marattiopsida (marattioid ferns), and Polypodiopsida or Leptosporangiatae (leptosporangiate ferns), and
  • b.) spermatophytes—all the other plant species that bear seeds such as gymnosperms and angiosperms
• Phylum Euphyllophyta

  Class Equisetopsida (Horsetails) - Plants under this class are characterized by reduced, whorled leaves with ridged stems having internal hollow canals.

  
  

  Family Equisetaceae (Horsetail/Scouring-Rush family) - This family houses one genus, Equisetum. This family is characterized by rhizomatous, perennial herbs bearing sporangia in terminal strobili that are homosporous.
• Phylum Euphyllophyta

  Class Psilotopsida - This Class houses two Orders, Ophioglossales and Psilotales. Gametophytes of both orders are nonphotosynthetic (heterotrophic), contain mycorrhizal fungi, and are often subterranean.

  
  

  ORDER OPHIOGLOSSALES (Ophioglossoid Ferns)

  Species in this order bear a eusporangium, a sporangium that arises from a group of epidermal cells.

  
  

  ORDER PSILOTALES (Whiskferns)

  There are two living genera, Psilotum (2 species) and Tmesipteris (˂30 species). Tmesipteris (hanging fork fern) while Psilotum (whisk broom).
• ORDER PSILOTALES (Whiskferns)

  Their leaves are very reduced and peglike; and may lack a vascular strand– hence, they serve as enations: an outgrowth from surface of a leaf. Their sporangia are two- or three-lobed organized into a synangium which turns yellow at maturity. They have rhizoids but lack true roots and often epiphytic, with rhizomes having mycorrhizal symbiotic associations.
• PHYLUM PTERIDOPHYTA

  Like the other cryptogams, they are spore-bearing and mostly homosporous. Their gametophytes are conspicuous though reduced, independent of the sporophyte and germinate outside of the spores (exosporic).
• Megaphylls - photosynthetic leaves with a more intricate vascular system.
• Megaphylls are associated with leaf traces and leaf gaps on the stem.
• Fern Adaptations

  • Such ferns that grow on rocks are epipetric.
  • Other ferns grow on tree trunks, branches and crown of trees and are known as epiphytic.
  • The lower leaves (bathyphylls).
  • The higher leaves (acrophylls) consist of the sporangia.
  • These leaves are often called as fertile fronds.
• Fern Anaatomy

  • Ferns consist of an underground stem known as the rhizome which is responsible for producing the roots and assimilation of nutrients and water from the soil.
  • The plant’s roots are connected to the blade by the stipe or stalk.
  • The part of fern stem that is within the blade is refer as the rachis or axis.
  • The blade is the leafy part of fern which bears the leaflets (pinna) and secondary or smaller leaflets (pinnule).
  • The frond refers to the whole leaf fern which consist the blade and the stalk.
  • Young fronds are known as fiddleheads as these resemble the head of a violin.
• Sori - this houses the spores. These are found on the underside of the blade.

  Indusium - this is a thin flap of protective tissue that covers the young sori.

  Spores -These tiny living cells are microns in size and can only be seen when in groups looking like a fine dust.