Abstract: A method for controlling the environmental conditions in the proximity of vegetation or crops in the cultivation of plants is described in which use is made of protective sheets comprising a large number of microperforations having each a protruded rim, said microperforations having a diameter between 50 and 2000 .mu.m and being present in a density of between 25 and 40000 microperforations per cm.sup.2. The invention also relates to plastics sheeting for use in said method and to a protective device for use in a greenhouse provided with such sheeting.

Abstract: The invention relates to a process of electroforming a metal screen by electrolytically depositing a metal upon a metal matrix, having recesses filled with insulating material, a separating means, such as beeswax, being provided upon the ribs bounding the recesses.The formed first screen skeleton is removed and subjected to an electrolysis in a second electrolytic bath for depositing the same or another metal upon the first screen skeleton.Finally from a third electrolytic bath a top layer of metal is deposited upon the layer deposited from the second electrolytic bath.In a preferred process the first electrolytic bath is a nickel bath, the second electrolytic bath is an iron bath or a bath of a nickel-iron alloy and the third electrolytic bath a nickel or nickel-tin alloy bath.The second and other or third electrolytic bath contain an organic compound improving deposit of metal or metal alloy substantially perpendicular to the surface of the skeleton.