10 Lines On My Family For Class 9 To 12

Essay on c2 level writing

Disputes in special receptacles – a sporangium are formed. At the lowest plants a sporangium monocelled, at the highest – multicellular. In a sporangium spore-forming fabric is formed. Cells of this fabric share by a mitosis or meiosis and form disputes.

Full life cycle of ferns consists of two phases – phases of a gametofit and a phase of a sporofit. When speak about ferns, mean first of all sporofit. As well as at the majority of the higher plants (except for Mokhovidny), sporofit ferns is the dominating phase in their life cycle.

During evolution there were most various forms of vegetative reproduction: reproduction by natural layers, reproduction by kornevvy offsprings, reproduction by specialized parts of plants – rhizomes, tubers, bulbs, land and underground hundred-bosoms, vyvodkovy kidneys.

Natural layers many species of trees and bushes breed: Fir, Fir-tree, Guelder-rose, Filbert and others. On branches of these plants in a place of contact with the soil additional roots that promotes emergence of new escapes and independent individuals are formed.

Widespread modification of escape are tubers. The tuber is the truncated escape serving for a reserve of nutrients and vegetative reproduction. From Far East plants reproduction by tubers is characteristic for types of the sort Crested bird, the Core which is three-made an incision, Sedmichnik, the Horsetail field and some other types.

Gametes in special bodies – gametangiya are formed. At the lowest plants of a gametangiya, as a rule, the monocelled. At the higher plants they multicellular. Man's gametangiya carry the name. Female gametangiya of the lowest plants are called as oogoniya, at the highest – arkhegoniya. Arkhegony is the multicellular education having a kolbovidny form. Consists of an expanded paunch and the extended neck. On the channel of a neck spermatozoa get to a paunch where merge with an ovum. It is most well developed arkhegoniya at mosses. Further its reduction is observed.

Disputes of ferns, as well as other higher plants, are formed of cells of spore-forming fabric as a result of reducing division. Similar disputes are called as. They consist of a haploid kernel, cytoplasm and two covers – ekzina and intina. The majority of modern ferns – plants ravnosporovy. They form one look dispute from which the oboyepoly grows gametofit. Representatives of three families Pteroid – Marsileevy (Marsileaceae), Salviniyevye (Salviniaceae), Azollovye (Azollaceae) – are raznosporovy plants. They form two types dispute – microdisputes and megadisputes which at germination form according to man's and female gametofit. All types of ferns with which we worked, are ravnosporovy. Having got to favorable conditions, disputes sprout. Humidity of the soil and air, warmly (from 15 to 30os), and also light are necessary for germination dispute. Disputes of the majority of ferns do not sprout in the dark.

At the lowest plants disputes are often supplied with zhgutika. They are called as zoodisputes. If disputes of the lowest plants are deprived of zhgutik, they are called as aplanospor. At the higher plants disputes never have zhgutik.