72 



REPORT OF THE SECRETARY. 



Panicnm latifolinm, L. 

 Panicuni microcarpon, Miihl. 

 Pauiciun dichotomum, L. 

 Panicum Crus-galli, L. 

 Setaria glauca, Beauv. 

 Setaria viridis, Beanv. 

 Erianthns saccharoides, Micbx. 

 Andiopogon fuscatus. 

 Audropogon Virgiuicns, L. 

 Equisetum hyemale, L. 

 Polypodium vulgare, L. 

 Pteris aquiliua, L. 

 Adiantum pedatnm, L. 

 Asplenium Tricboinanes L. 

 Asplenium ebeneuni, Ait. 



Asplenium tbelypteroides, Micbx 

 Asplenium Filis-fcemina, Bernb. 

 Pbegopteris bexagouoptera, Fee. 

 Aspidium Novaboracense, Swartz. 

 Aspidiura Filix-mas, Swartz. 

 Aspidium acrosticboides, Swartz. 

 Cystopteris fragilis, Berub. 

 Onoclea seusibili. 

 Dicksouia pilosinscula, Walld. 

 Botrycbium teruatum, Swartz, var. obli- 



quum, Milde. 

 Botrycbium teruatum, Swartz, var. dis- 



sectnm, Milde. 

 Botrycbium Virginiauum, Swartz. 

 Lycopodium complanatum, L. 



GEOLOGY OF THE ZOOLOGICAL PARK. 



A special report upon tbe geology of tbe Park bas been kindly furnisbed by Mr. 

 W. J. McGee, geologist to tbe Geological Survey. 



" Tbere is transmitted berewitb a geologically colored map of tbe National Zoolog- 

 ical Park. 



"Except tbat tbe prevailing rock formation is complex in structure and of age not 

 yet definitely determined, tbe geology of tbe Park is exceedingly simple. Tbe for- 

 mations are: 



Recent Alluvium. 



Pleistocene Columbia loam and gravel. 



Cretaceous (?) Potomac gravel. 



S Piedmont gneiss. 

 Vein quartz. 

 Steatite. 

 "In addition to tbese well cbaracterized formations tbere is a limited variety of 

 residua left on decomposition of rock in place, of torrential or overplacement depos- 

 its formed by wasb adown slopes, etc. 



"Tbe recent alluvium is confined to tbe cbannel and flood plain of Rock Creek. It 

 consists of loam, sand, and gravel partly derived from tbe older formations witbin 

 tbe Park, but mainly brougbt in by Rock Creek from beyond tbe limits of tbat reser- 

 vation. Tbese materials are sometimes irregularlj' stratified, but again assorted into 

 sbeets, sand-banks, gravel-bars, and more extended stretcbes of loam. It sbould be 

 observed tbat tbe alluvium area, togetber witb tbe cbannel meandering turougb it, 

 are coterminous witb tbe flood plain of Rock Creek, and hence are subject to over- 

 flow during great fresbets. 



" Tbe Columbia formation is a deposit of loam, gravel, bowlders, etc., formed dur- 

 ing tbe first ice invasion of tbe glacial period. Its age is tberefore early Pleistocene. 

 About rivers tbe formation commonly consists of two members, tbe upper a bomoge- 

 neous loam commonly red or brown in color, and tbe lower a bed of sand, gravel, 

 cobble-stones, and bowlders commonly stained brown by ferric oxide, sometimes 

 stratified, and bere and tbere displaying a peculiar black stain wbicb is mainly fer- 

 ruginous, but bas been found to contain a trace of cobalt. Along tbe rivers of tbe 

 Middle Atlantic slope tbe formation is sometimes fiisbioned into terraces; and some 

 of its best developments in tbe District of Columbia (from wbicb tbe name is taken) 

 are terraciforra. In the Park tbe deposit displays tbe tisual division into a superior 

 loam and an inferior bed of coarse materials; and the usual topographic form is as- 

 sumed since tbe deposit is practically confined to tbe pine-clad terrace or bench north 

 and west of Rock Creek, in tbe central part of tbe reservation. Tbe formation is in- 

 deed confined to these terraces, save tbat an ill-defined and perhaps scarcely continu- 



