Tab A - Page 46 
major mechanism for the process requires Ice nuclei to Initiate Ice formation 
In some of these droplets which then increase in size by collision with other 
droplets of supercooled water or by deposition of water vapor on the particles 
that have a lower vapor pressure than supercooled water at the temperatures 
from -5° to -20° C In clouds. The most abundant and only detectable Ice nuclei 
found In the atmosphere to date are inorganic particles. (T) 
Much circumstantial evidence indicates ice-nucleatlon-actlve bacteria may 
be Important in atmospheric precipitation processes. Several researchers have 
suggested that Ice nucleation-active bacteria may be Important In atmospheric 
precipitation processes because they contribute ice nuclei active at warm 
temperatures (lindow et al., 1975b; Maki et a!. t 1974; Schnell et al . , 1981; 
Vali and Schnell, 1975; Zankofsky, et al . , 1981). P_. _s. syrlnqae have been 
shown to be active as ice nuclei as aerosols in cloud chamber tests that are 
similar to conditions found in the atmosphere (Maki and Willoughby, 1978; 
Schnell, 1976; Schnell et al., 1981). Thus, since ice-nucleation-actl ve 
bacteria have been reported in significant numbers In the atmosphere, there 
is good circumstantial evidence that plant sources of Ice-nucleation-active 
bacteria may be important as atmospheric ice nucleants and thus as a factor 
in determining global climatology by affecting worldwide precipitation 
processes. (T) 
It is conceivable that £. s.. £v. syrinqae and other Ice-nucleatlon-actlve 
bacteria would derive a survival benefit from nucleating Ice formation In the 
atmosphere. Assuming that Ice-nucleatlon-actlve bacteria would benefit by 
distribution on leaf surfaces by long-distance transport In the upper 
atmosphere, factors Increasing the survival of these bacteria during this 
43 
[ 240 ] 
