POLLEN AND SPORES — LEOPOLD AND SCOTT 



309 



deposition. Transportation by rivers, as well as by wind, may be re- 

 sponsible for the intermingling of pollen derived from entirely dis- 

 tinct ecological assemblages. 



The interplay of these factors has been illustrated by a study of 

 the modern pollen fallout at Eagle Lake in northern Maine (Hyland 

 et al., 1953). The aerial pollen fallout in 1950 was measured by 

 counting the numbers of different pollen and spore types falling on 

 a "sticky slide" exposed for daily intervals during the growing season 

 (fig. 4). 



172 



2 °0 Kfomef, 



ers 



Figure 3. — Pine pollen fallout (number of grains per square centimeter) at mountain sta- 

 tions in Norway during the growing season of 1942. Stations within the forest area 

 accumulate much more pollen than those near timberline. (From Faegri and Iversen, 

 1950.) 



The results show first that pollen rain is actually a series of fall- 

 outs that occur during the blooming periods of different local plant 

 types; the trees release pollen in the spring, and grass pollen, weed 

 pollen, and fungal spores appear during middle and late summer. 

 Coniferous trees numerous in the local forests (pine, spruce, and 

 cedar) contribute heavily to the total yearly average, but oak and 

 elm, rare types in the local stands, are poorly represented in the 

 pollen rain at this site. 



All the spore and pollen types shown in figure 4 are wind trans- 

 ported except maple and willow, which grow in profusion on nearby 

 ridges. These are rather meagerly represented in the yearly average 

 pollen rain in comparison with their density in the vegetation at the 

 immediate site. Insect-pollinated plants including maple and willow 



