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Stipes AND PODETIA. 
Very naturally, we may consider next in order podetia and stipes. Both are 
to be regarded as structures developed originally for the purpose of supporting 
the spore-bearing organ, or apothecium, and raising it up into the air. But 
in the Cladonias and Stereocaulons , a secondary function has replaced the 
original to some extent, and the original stipe, a structure devoid of algal 
cells as that of the Caliciums , Cypheliums and Coniocybes, has in these first 
two genera taken to fostering the algal cells, thus becoming a true thallus, 
whose vertical expansion and often extensive branching greatly increases the 
area of surface below which the algae may find protection. Thus the stipe 
differs from the podetium in that the former is devoid of algal cells and the 
latter not, the former belonging to the fruiting tract, and the latter, doubt- 
less by modification, more properly to the vegetative tract. 
Rhizoids and Cilia. 
And after thus considering the gross morphology of the thallus and the 
fruiting tracts, there are a number of less conspicuous structures, less con- 
stantly present even than the fruit, or not so often to be seen with eye or 
lens, but still sometimes quite apparent. First among these may be men- 
tioned the rhizoids and cilia. The rhizoids are found on the ventral side of 
most foliose thalli and serve as attaching organs. They appear to the eye as 
root-like bodies, varying in color from white to black. We say root-like, but 
do not call them roots, since they differ from true roots very much as to 
minute morphology. The cilia are like the rhizoids in structure, but are 
found on the upper surface of the thallus or along the margins. 
The hyphal rhizoids of the crustose lichens are quite different morphol- 
ogically, but these need receive no attention here on account of their minute 
size. However, it is in order to state that the functions of cilia are to retain 
drops of water and gradually absorb them, and sometimes when quite num- 
erous, to protect against cold and dust. Closely related to rhizoids is the 
simple attaching organ on the ventral sides of the thalli of Gyrophoras, 
Umbilicarias, and many Endocarpons. This structure is known as the 
umbilicus. 
Some Other Structures. 
Spermagonia, soredia, cephalodia and cyphellae are structures which 
occur on the surface of thalli. The spermagonia are organs of doubtful 
nature and function, sometimes quite conspicuous as dark colored spots on 
the upper surface of the thallus as in some Parmelias and other large 
foliose lichens ; but these structures are more often minute and of the color of 
the thallus so that they appear only in sections. They were formerly 
thought to be of considerable value in the determination of species. The 
soredia are little powdery masses, usually whitish in color, and scattered over 
the surface of the thallus as in Pyxine sorediata and many other 
lichens. Cephalodia are wart-like bodies found on the upper surface of some 
lichens as in Peltidea aphthosa , or within the thallus, as in some other lich- 
ens. Cyphellae are small pits or depressions in the lower surface of some 
foliose lichen thalli as in some Stictas and Stictinas. The further consider- 
