300 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



Associated with the foregoing are species of Codiaceae (Girva- 

 nella, Sphaerocodium, Haliineda, Ovulites), Dasycladaceae (Aci- 

 cularia, Cymopolia, Venniporella, Diplorella, Gyroporella). The 

 Characeae, or Charophyta us they are sometimes called, are a 

 somewhat isolated group of fresh and brackish water forms, the 

 stoneworts. They are doubtfully recorded from rocks as old as the 

 Devonian and their calcareous fruits (oogonia) are present in con- 

 siderable abundance throughout the Mesozoic and Cenozoic. The 

 Rhodophyceae (Florideae), or red algae, include one family, the 

 Corallianceae, that is of considerable geological importance, being 

 represented as early as the Ordovician by Solenopora, and common 

 throughout the Mesozoic and Cenozoic (Lithothamnium, Lithophyl- 

 lum). These are the nullipores or reef-forming types and some of 

 them are remarkable in that they contribute as much as 25 per cent 

 of magnesium carbonate to the resulting reefs. 



Paleozoic bacteria have been known since 1879, and a considerable 

 number of supposed species have been described by Renault. Pro- 

 terozoic bacteria have recently been described by Walcott, who 

 believes that pure limestones without traces of organisms other than 

 algae clearly indicate the presence of bacteria as the active agents 

 of precipitation through their denitrifying activities. Traces of 

 fungi are commonly met with from the Devonian onward. These 

 are usually in the form of mycelial hyphae, both nonseptate 

 (Phycomycetes) and septate (My corny cetes). They occur in fossil- 

 ized plant tissues, and occasionally the minute spores or traces of 

 oogonia or sporangia are present. Berry has recently described 

 forms in petrified Eocene palm wood in which various stages of 

 sporangial growth and spore formation are preserved (Peronos- 

 poroides). Other specimens show zygospores or conidia (Zygospor- 

 ites, Cladosporites, Haplographites, Oochytrium, etc.) 



Foliage preserved as impressions frequently shows traces of leaf 

 spot or other fungi, and many undoubted remains of this sort have 

 been described. All of these types of fungal remains are exceedingly 

 common at all horizons where petrified or other plant tissues occur, 

 but their nature largely precludes systematic study. It can be safely 

 asserted that the fungi were of very ancient origin and were already 

 present in great variety in the older Paleozoic, but that their perish- 

 able nature and nonaquatic habitat has prevented large numbers 

 from becoming preserved as fossils. Microscopic forms of both algae 

 and fungi are present in abundance in oil shales and in some bog 

 ores of iron from the Silurian down to the present time. 



PHYLUM BRYOPHYTA. 



The Bryophyta or moss plants, comprising the existing mosses and 

 liverworts {Hepaticae) , which occupy so prominent a place in some 



