① Seed Dispersal and Pollen Dispersal
Unlike animals, plants are limited in their ability to seek outfavorable conditions for life and growth. As a result, plants haveevolved many ways to disperse their offspring by dispersing theirseeds. A seed must somehow "arrive" at a location and be there at atime favorable for germination and growth. Commonly there are twoways for seed to spread. First, wind dispersal of seeds, oranemochory, is one of the more primitive means of dispersal. Winddispersal can take on one of two primary forms: seeds can float onthe breeze or alternatively, they can flutter to the ground. Someseeds (e.g., pine) have a wing that aids in wind dispersal. Thedust-like seeds of orchids are carried efficiently by the wind.Some seeds, (e.g. milkweed, poplar) have hairs that aid in winddispersal. Second, it disperses by animals. Seeds (burrs) withbarbs or hooks (e.g. acaena, burdock, dock) which attach to animalfur or feathers, and then drop off later. Seeds with a fleshycovering (e.g. apple, cherry, juniper) are eaten by animals (birds,mammals, reptiles, fish) which then disperse these seeds in theirdroppings. Seeds (nuts) are attractive long-term storable foodresources for animals (e.g. acorns, hazelnut, walnut); the seedsare stored some distance from the parent plant, and some escapebeing eaten if the animal forgets them.
And a related process to seed dispersal is anemophily, which isthe process where pollen is distributed by wind. Large families ofplants are pollinated in this manner, which is favored whenindividuals of the dominant plant species are spaced closelytogether. Pollen in plants is used for transferring haploid malegenetic material from the anther of a single flower to the stigmaof another in cross-pollination. In a case of self-pollination,this process takes place from the anther of a flower to the stigmaof the same flower. Due to the natural selection, some plants onlyproduce pollen in the spring in order to be distributed.
With respect to the history of oil painting, most Renaissanceparticular Vasari, credited northern European painters of the 15thcentury, and Jan van Eyck in particular,with the "invention" of painting with oil media on a wood panelsupport ("support" is the technical term for the underlying backingof a painting). However, Theo clearly givesinstructions for oil-based painting in his treatise, On VariousArts, written in 1125. At this period it was probably used forpainting sculptures, carvings and wood fittings, perhaps especiallyfor outdoor use. Early Painting in the 15thcentury was, however, the first to make oil the usual paintingmedium, and explore the use of layers and glazes, followed by therest of Northern Europe, and only then Italy.
Early works were still panelpainting on wood, but around the end of the 15thcentury canvas became more popular as the support, as it wascheaper, easier to transport, allowed larger works, and did notrequire complicated preliminary layers of gesso (a fine type ofplaster- this style was known as a fresco painting; applying gesso,then painting over with the tempera paint) Venice, wheresail-canvas was easily available, led the move. Smallpaintings were also made on metal, especiallycopper plates. These were more expensive but very firm, allowingvery fine detail; often printing plates from printmaking werereused. The popularity of oil spread through Italy from the North,starting in Venice in the late 15th century. By 1540, the previousmethod for painting on panel, tempera, had become all but extinct,although Italians continued to use fresco for wallpaintings, which was less successful and durable in damper Northernclimates.
Italy was not the first country where oil paintings were madebut Norway where paintings were used to decorate churches there. Afamous Italian artist once believed that such techniques wasintroduced from Germany. People in Venice loved this art form mostand citizens in Florence showed greater enthusiasm for that theythought that oil paints provided bright colors and allowed them torevise their initial planning when painting.