The Collemaceae of Ohio 
45 
of which is usually like that of the exciple into which it is produced, and 
a hymenium composed of the asci and the paraphyses, the former blue 
and the latter yellow-brown in iodine; spores simple, several-celled, or 
muriform, brown in iodine; apothecia usually surrounded by a thalloid 
margin. 
The algal host is a form of Nostoc and is strongly modified and 
transformed into a more or less plainly foliose structure, which has 
peculiar features of form, size, or color dependent on the transforming 
efifect of the particular lichen parasite. The algal-host colony becomes 
gelatinous when wet, and the gelatinization is more marked when the 
alga functions as the host of a species of the CoUcinaceae which is devoid 
of a cortical plectenchyma. 
KEY TO THE OExXERA 
Without a typical plectenchymatous cortex. 
Spores 2- to several-celled. Synechoblastus 
Spores muriform. Collema 
With a typical plectenchymatous cortex. 
Rhizoids not plainly noticeable with the hand lens. Leptogium 
Rhizoids plainly noticeable with the hand lens. Mallotium 
Synechoblastus Trev. Caratt. Gen. Collem. 2. 1853. 
Transforming the algal-host colony into a blue-green, olivaceous, or 
nearly black, irregular or foliose body, with the lobes often ascending or 
erect and covering the horizontal portions, often to the center of the 
colony; thallus not differentiated into a typical plectenchymatous cortex 
and a mycelia medulla, but the whole structure commonly mycelial and 
the hyphse usually more densely disposed toward the surfaces, especially 
the upper surface; hyphse hyaline, perpendicular, horizontal, and extend¬ 
ing in various directions, straight or curved, monopodially branched; 
rhizoids inconspicuous, but commonly seen in sections of some of the 
species; apothecia scattered; disk flat to convex, red-brown to black- 
brown, surrounded by a thalloid margin which is sometimes overgrown; 
exciple either densely mycelial or plectenchymatous, usually tinged with 
brown; hypothecium similar in structure and color; hymenium hyaline 
below to pale- or darker-brown above; paraphyses hyaline at the base 
and gradually becoming tinged with brown toward the enlarged apex, 
simple or once to several times monopodially branched toward the a])ex 
or farther back, all species examined showing both simple and liranched 
