105 



and wrinkles. Tips take a paw-like shape with upper surface 

 moderately dark green, bordered with a whitish line where it 

 meets the under surface. This under surface is black, roughened 

 by tiny papillae standing close together, and visible as a nap 

 under a strong glass, but with weaker magnification, showing 

 only as a dull finish, in contrast to the shining under-tips of P. 

 physodes. 



Fruits are usually rather abundant, scattered along the older 

 trunks and branches, bowl-shaped, chestnut-brown or darker, 

 with a thick, smooth, pale rim. They are of all sizes up to 8 mm. 

 diameter, and when large are often of irregular shape. The 

 spores, undivided, colorless, very small, 3 to 6 by 1 to 2 rrticrons, 

 are numerous in the spore sack, instead of numbering only 8, as 

 in most Shield Lichens, and are usually shaped like a curved 

 sausage. 



Under the microscope, P. colpodes is easily differentiated 

 as the only local Shield Lichen with more than 8 spores in the 

 spore-sack, and the only one with curved spores. With a hand 

 lens alone however, it can be determined definitely, because no 

 other local lichen of this type has the black nap under the tips, 

 which is perhaps 0.1 mm. deep, and not at all like the much 

 longer blackish holdfasts of such lichens as Physcia endochrysea. 

 The presence of fruits and the absence of sorediate tips dis- 

 tinguish it at once from P. physodes and P. pertusa. From Phy- 

 scia stellaris and Cetraria placorodia, its darker color and black 

 under surface easily separate it. 



Parmelia olivacea. Olive-Browx Shield Lichen. 



Rather frequent everywhere on trees where other Shield 

 Lichens grow, P. olivacea often escapes notice because its color 

 does not differ greatly from that of the bark. It spreads irregu- 

 larly, flattening against the foothold, and the tips of the lobes 

 often widen to 5 mm. or even more, but very thin, in contrast to 

 the puffed lichens just described. About 1 cm. or so behind the 

 tips, it often becomes a thin shapeless crust with confused wrin- 

 kles instead of radiating branches. Near the tips, the color is 

 yellowish-brown to chestnut, or olive when wet, often shining 

 like bronze metal, while older parts may blacken, or show dots 

 of whitish soredia, or white where the brown surface has been 

 scratched off. The under surface is dark brown or black. 



