TORREYA 



Vol. 19 No. 5 



May, 1919 



A NEW RICCIA FROM PERU* 



By Alexander W. Evans 



Through the kindness of Mr. W. R. Maxon, of the United 

 States National Museum, the writer has received for study an 

 interesting collection of Peruvian Hepaticae, made by Messrs. 

 O. F. Cook and G. B. Gilbert in 191 5. One of the most re- 

 markable of the species represented is the Riccia noted below, 

 which seems to be undescribed. The remaining species are not 

 yet wholly determined, so that a complete account of the col- 

 lection can not be published at the present time. 



Riccia bistriata sp. nov. 



Plants growing in irregular patches: thallus simple or once 

 or twice dichotomous, strap-shaped to obovate, mostly 0.5- 

 1.5 cm. long, 2-4 mm. wide, and 0.5-0.6 mm. thick in the median 

 portion, distinctly areolate and dull green above, a marginal 

 band becoming bleached with age, more or less pigmented with 

 purple below, especially toward the margin, median sulcus in 

 the apical region only, 1-1.5 mm. long, the older portions of the 

 thallus plane or nearly so above and convex below, gradually 

 thinning toward the margin, where the two surfaces meet at an 

 acute angle; ventral scales inconspicuous, hyaline, scarcely pro- 

 jecting beyond the margin ; cells of the primary dorsal epidermis 

 subhemispherical, the upper part soon collapsing and disappear- 

 ing, leaving the basal portion in the form of a thickened shallow 

 cup; green tissue of the usual Riccia type, consisting of upright 

 rows of cells separated by narrow (usually) four-sided canals 

 not constricted at the dorsal surface of the thallus, each row of 

 cells usually connected longitudinally with four other rows and 

 composed of five or six cells, the longitudinal walls common to 

 two rows being marked by two colorless bands, of thickening 



* Contribution from the Osborn Botanical Laboratory. 



[No. 4, Vol. 19 of ToRREYA, Comprising, pp. 57-84, was issued 25 June, 19 19] 



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