Habit is the external form of a plant taken as a whole. It is usually described by a few general adjectives, such as erect, open, spreading, etc. However, to study the inheritance of plant habit, a detailed analysis of the real characters underlying habit must be made. It is usually found that the general outer appearance of a plant, its habit, is the result of a combination of independent characters, units, the recombination of which by crossing often results in plants much altered in appearance from the parent varieties. Characters usually unimportant may be found of primary importance in the formation of plant habit.