116 
PLANT STUDIES 
FIG. 118. Winged fruit of 
Ailanthus. After KER- 
NER. 
reports of "showers of sulphur" have 
arisen from an especially heavy fall of 
pollen that has been carried far from 
some gymnosperm forest. In the case 
of pines and their near relatives, the 
pollen spores are assisted in their dis- 
persal through the air by developing a 
pair of broad wings from the outer 
coat of the spore (see Fig. 110). This 
same method of pollination that is, 
carrying the pollen spores by currents 
of air is also used by many mono- 
cotyledons, such as grasses ; and by 
many dicotyledons, such as our most 
common forest trees 
(oak, hickory, chest- 
nut, etc.). 
78. Dispersal of 
seeds by air. Seeds 
are very rarely light 
enough to be carried 
by currents of air 
without some special 
adaptation. Wings 
and plumes of very 
many and often very 
beautiful patterns 
are exceedingly com- 
mon in connection 
with seeds or seed- 
like fruits (see Figs. 
115, 116, 117, 118, 
119). Wings are de- 
veloped by the fruit 
FIG. 119. Fruit of basswood (Tilia), showing the 
ash, and by the Seeds peculiar wing formed by a leaf. After KERNER. 
