Water is essential for life and without water no life exists. The liquid sur- rounding of an aqueous solution is the conditio sine qua non for most of the physiological responses and as such, water is as decisive for the occurrence of a single enzymatic reaction as it is for the global zonation of world vegetation. It is no wonder that scientists since early times have made every effort to describe and understand the functional interrelationships between water and the phe- nomenon of life. During the past half of this century, these endeavours in the field of botany have been marked by steps...