class filicinae example of adiantum and its life cycle


all the plants that belongs to this group are collectively known as the ferns 


  • plants belonging to this group are found all over the globe bu they have their most concentration in tropics 
  • almost of them are found in moist and shady places but some of them can also grow in dry conditions 
  • they can grow in both hilly areas and in plains 
  • some of them are epiphytic and grow on the bank of rivers such that they are parasites such that they can greatly vary in size 
  • they contain foliar sporangia such that sporangia attached to leaves such a type of leaves are known as fronds when the frond is young and immature they are coiled and this specific pattern of them is known as circinate vernation 

example of important ferns are 

  • dryopetris
  • pteridium 
  • adiantum 
  • pteris  


*it is also known as the Maiden Hairfern  
*adiantum is a common example of fern that belongs to the class filicinae 
*it usually grow along moist walls water courses and drains 
*it is a small herb that usually consist of stem roots and leaves 
*in them the stem is short thick underground usually branched horizontally growing rhizome
*in them the rhizome is protected by brownish scales called as the ramenta and is covered by persistent leaf basis 
*in them the fibrous adventitious roots arises from the lower side of the rhizome 
*compounds leaves or fronds arises from the upper side of rhizome young leaves show circinate vernation 
*the stipe (stalk) and rachis of leaf are black smooth shiny that is the reason it is also known as the maiden hairfern 
*the leaflets (pinnae and pinnules) show dichotomous venation
*sori(group of sporangia) are born on the underside of the reflexed lobes of the margins of leaflets and are protected by bend margins of the leaflets forming false indusium 
life cycle of adiantum 
*adiantum have hetromorphic alternation of generation in which 
*sporophyte being dormant on the gametophyte  
*gametophyte is small znd reduced but are separate and independent  
structural features of sporophyte 
different structural features of sporophyte of adiantum are
*the diploid sporophyte produces a number of sori(singular sorus) when the sori are formed they are green but they turn dark brown when they mature 
*each sorus consist of a number of sporangia that are covered by false indusium the leaves bearing sporangia are known as the sporophylls
*each of the sporangium is slightly flattened biconvex body (capsule) born on a multi cellular stalk the capsular layer consist of a single layer of flat thin walled cells the edge of the capsule is made up of two parts that are annulus and stomium  
*the annulus occupies three fourth of the edge annular cells have their radial and inner walls thickened 
*whereas the stomium occupies one fourth of the edge the stomial cells are very thin 
conversion of sporophyte into gametophyte 
*inside each of the sporangium haploid spores are produced by meiosis that is also known as the reductive division of diploid megaspore mother cell
*the annulus of the sporangium contracts in dry weather the stomial being thin walled rupture and spores are dispersed by wind 
*when a spore falls on ground on a moist soil than it germinates at a suitable temperature and produces a haploid gametophyte or prothallus
structural features of gametophyte 
different structural features of gametophyte generation of adiantum are  
*the prothallus is an autotrophic small flat heart shaped structure
*at anterior end of the prothallus is a notch in which lies the growing point its size is about one third of an inch at its longest diameter 
*it is horizontally placed on the ground and has unicellular rhizoids on its lower surface towards the posterior end the rhizoides fix the prothallus to the soil and adsorb nutrients for it 
*it is composed of rounded thin walled cells the margin of the prothallus is one cell thick but the middle part is many celled thick and is cushion like 
*it is monoecious such that male and female sex organs appear on the underside of the same prothallus in the mature prothallus archegonia occurs near the notch and the antheridia are scattered among the rhizoids 
*the archegonium consist of a ventor and a neck the ventor contains the egg and is embedded in the cushion of the thallus 
conversion of gametophyte generation to sporophyte generation
each antheridium produces numerous spermatozoids which are spirally coiled and multiciliated they reach the archegonium by swimming in water fertilization occurs and an oospore is formed the oospore is formed the oospore forms the sporophyte young sporophyte is first attched to the gametophyte but later becomes independent


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