Abstract
This paper attempts to provide an introduction to daylight and the manner in which it can vary, with particular reference to arboriculture and forestry, and with some reference to architecture and planning. There appear to be very few sources of information which provide a comprehensive and readily understandable description of the variables that influence the amount of daylight which is received at any particular point and the effects that this is likely to have on plant growth and the provision of light within buildings. The author has attempted to relate direct measurements of daylight in different locations and at different times of the year to the limited amount of published information that he has been able to find, in order to provide an overview of this somewhat complex and frequently misunderstood topic.