Mosses and Lichens 



The generic name Peltigera from the Latin pelta, a shield, and 

 gerere, to carry, refers to the fruits which are shield-shaped with 

 a more or less scalloped border; they are borne close to the upper 

 surface of the thallus, usually some distance back from the margin 

 but occasionally on the margin. 



The spores are long and narrow, four- to many-celled, at 

 length colourless. It is a small genus of mostly cooler regions. 



The Dog Peltigera, Peltigera canina, (L.) Hoffm. See 

 Colour Plate VII. 



Habit and habitat. This lichen grows in extensive patches 

 on logs or on the ground. 



Vegetative organ (thallus). Large greenish-gray, ashy, or 

 brownish: membranaceous, round-lobed; furrowed and downy 

 on the upper surface: whitish beneath with light-coloured veins 

 and hairs, sometimes becoming dark. 



Fruiting disks (apothecia). Reddish-brown; of large size; 

 rounded, becoming semi-revolute and vertical. Supposed to 

 resemble dogs' teeth and for this reason, on the supposition that 

 "Like cures like," used as a remedy for hydrophobia. 



Name. The specific name canina from the Latin canis, a dog. 



Spores. Somewhat needle-shaped; four- to eight-celled. 



Peltigera aphthosa, (L.) Hoffm. and P. polydactyla, (Neck.) 

 Hoffm., are quite similar in general appearance to P. canina, (L.) 

 Hoffm. P. aphthosa however, has the thallus smooth above, 

 more or less sprinkled over with brown warts, and contains green 

 algae, not blue-green as in the two following species. P. poly- 

 dactyla differs from canina in being smooth above and nearly 

 naked beneath and conspicuously reticulated with brown veins. 



Genus STICTA (Schreb.) Fr. 



The thallus is leaf-like, variously lobed but with the lobes 

 usually wide, rounded, or elongated. The under surface is some- 

 times smooth but is commonly covered with short, soft hairs 

 (vtllous), and dotted with little cups or rounded heaps (cyphels). 

 A cross-section of this lichen shows that the irregular, coloured 

 zone (gonimous layer) is composed of either green cells (gonidia) 

 or bluish-green cells (gonimia). 



The fruiting organs (apothecia) are shield-like (scutcllceform), 

 elevated, and near the margin of the thallus. 



86 



