IOWA ACADEMY OF SCIENCES. 65 



to July of the present year (1893). That is to say, our North •American Cycads 

 were represented up to that time by one living species, about a score of fossil 

 species from the Dakota group of the west, known to Lesquereux by more or less 

 fragmentary leaf casts, such species as Herr, of Lausanne, had described by leaf- 

 fragments from Greenland, and Tyson's two trunks, siliciSed, but withal poorly 

 preserved, kept in the museum at Baltimore. 



In July of the present year the writer, being in Hot Springs, South Dakota, 

 came across a handsome fossil offered for sale. The fossil proved to be a magnifi- 

 cently preserved, silicified Cycad. Some days later, on a bare hill, about thirty 

 additional specimens were found in a more or less perfect state of preservation. 

 Time has not as yet permitted a microscopic examination of the Dakota specimens, 

 but all macroscopic characters are decidedly those given in Dr. Carruthers' definition 

 of his genus. Our form is referred to a new species; for, while very much like B. 

 gihsonianua, of Carruthers, it yet differs in the distribution of the leaves, as well 

 as in the distribution of fibro-vascular elements of the leaf-petioles themselves. 



That the Maryland specimens are also members of the genus seems, as already 

 stated, most probable. It will be remembered that Mr. Fontaine, in his descrip- 

 tion calls attention to the flower buds bursting through the cortex, and to the 

 elliptical section of the fossil. Mr. Fontaine claims two sorts of buds on the 

 Maryland specimen but offers no microscopic sections in proof of the claim, besides 

 his specimens it would seem are too far weathered to allow the exact determination 

 of such points. These specimens cannot represent the genus Mantellia for in this 

 genus the stems are globular. In fact, the Maryland and Dakota forms are very 

 closely related — are probably species of the same genus and that: genus is, in the 

 writer's opinion, neither Ti/sonia nor Mantellia. Microscopic characters indicate 

 two distinct species, but microscopic details as yet are lacking for definite and con- 

 clusive comparison. It is hoped later to offer the Academy the microscopic char- 

 acters of the Dakota species. 



For further details, descriptions and figures the reader is referred to the Amer- 

 can Geologist for October, 1893, and to the Bulletin of the Laboratories of Natural 

 History, volume II, No. 4, State University of Iowa. 



RHUS TYPHINA Linn. 



BT T. H. M BRIDE. 



{Abstract) 



Rhus typhina is a northern plant, ranging from New Brunswick to Minnesota. 

 It comes into Iowa in the northern counties only, being found in Allamakee and 

 Clayton counties, hut, so far as reported, nowhere else. The plant along the bluffs 

 of the Mississippi river rises to a height of some thirty feet and has a stem at 

 base six inches in diameter. It is a beautiful shrub or tree, differing, at sight, by 

 its velvety branches and long-pointed leaflets, from the ordinary sumac {Rhus gla- 

 bra L.) and well worthy a place in our dooryards to say nothing of a wider and 

 better acquaintance. Where it prevails it seems to exclude the other species. I 

 have never found R. typhina and R. glabra on the same hillside. That the plant 

 should extend down the Mississippi river on the bluffs to McGregor and Lansing 

 or thereabouts and not go farther south along the same stream is an interesting 

 fact in connection with the problems ot plant distribution. 

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