Needle (from Latin vulgar acucula , diminutive of acus needle ) is the term used in botany to designate stings fine and delicate that they are not hurtful. 1 2 By extension, the bodies are those needle-shaped long and thin, especially the leaves of the pines , which is simply called "needles". 2 3
In other disciplines such as zoology or mineralogy also used this term, referring always to organs or other long, thin and pointed.

The akinetes are a specialized type of cells that produce some cyanobacteria in response to unfavorable living conditions.
Originate from cells which become larger with a wall thicker than vegetative cells, sometimes with small bumps; possess a cytoplasmic granular due to the accumulation of large amounts of cianoficina as reserve substance. Between the wall and mucilage layers secrete a new fibrous cap. They have a reduced metabolism and germinate when conditions are again suitable.

The land and air layering are an artificial method of plant propagation , which is to enable the emergence of roots . The layering is forced by heat, moisture from the soil prepared and incisions or fastenings to bent branches take root thereby forming new individuals endowed with properties identical to those of plant derived.
The layered branches take root more readily the more tender it is wood and wood fibers are further apart which is explained taking into account that all operations of layering only aim to stop and direct the sap to the branch or branches that are layered.
Although the layering is practiced in all seasons, the season is the most suitable spring being the time when the sap begins to move. The land to which the layering is done must be very substantial, soft and fresh, with obligatory if covered with mulch or other material that holds moisture.

Two types of layering:

The simplest method of layering is to pile up around the plant a piece of land forming convexity, which is what is called atetillar the plant . Piled earth, should be cut close to the same plant the outgoing to facilitate the formation of roots. Are obtained by this means as many new plant stems had and without prejudice to the mother plant continue sprouting again.

Layers on arc or Mugrn are generally used to play shrubs whose wood is very hard and are made ??before the plant opened a trench or excavation small, curving toward this part of it you want to lean out, taking care not to break and held then with a forked stick or cane, land, etc..
The layering of sierpecilla , meandering or wavy, unlike the preceding only in that the branch bent rather than cut out of the land becomes a hunch to go further, repeating this as many times as possible within its length. Are layered so that bushes gnarled root easily.
A variant is called layering by cutting and underpinning . This technique is commonly used to reproduce patterns from a "mother plant". It basically consists of topping the plant at ground level and, as they grow the various branches, it is accumulated dirt on them, forcing the emission of roots. When these roots are sufficiently developed, re-descalzar the plant, cutting each of the branches, which are a pattern identical to the parent plant.

Where layering is very thick branches and too high to be able to bend it goes to other more complicated procedures, either with ligatures stopping the course of the sap, and damaging or removing part of the bark of the plant in order to facilitate formation of nipples that root. Usually, these are air-layers in baskets, bags or pots called to layer so that the cross arm and projecting above and below.
Plants with woody stems scrape the layering is a young branch, before being sprinkled with hormones , forming roots and moss moist by generating short branch roots and transplanted .
The species of layering in each case must be set taking into account the nature of the plants, the age of the stem or outbreak, the state of the atmosphere and many other circumstances.