288 TRANS. ST. LOUIS ACAD. SCIENCE. 



in size in the same sporangium ; large and small ones are indiscriminately 

 mixed ; and they are also remarkably variable in their sculpture, showing 

 distinct or confluent vermiculate tubercles, or a nearly smooth surface ; 

 the dividing ridges or commissures are very prominent and smooth. The 

 leaf-bases of the typical form of this species are black and shining, and 

 justifv the name given by that zealous botanist, Jacques Gay, who in his 

 75th year was still anxious and able to climb the high mountains in the 

 centre of France, to study in their lakes the two European species which 

 had iust then become prominent through the labors of his friend Durieu 

 de Maisonneuve, and who left us such a vivid description of his hardships, 

 excitements and pleasures on that trip (Bull. S. B. F. vols. 8 & 9) ; death 

 prevented him from publishing it, but his name remains connected with 

 it. Now and then a paler specimen is seen, and the Texan form is always 

 pale, and distinguished also by its broader velum. 



13. I. BuTLERi, Engelm. Dioecious, smaller than the last, with a 

 subglobose trunk and thinner and more rigid bright green leaves, 8 to 12 

 in number and 3 to 7 inches long; sporangium usually oblong, spotted, 

 without any or with a very narrow velum; ligula subulate from a trian- 

 gular base; macrospores larger than in last, 0.50 to 0.63 mm. in diameter, 

 similarly marked with knobs or warts, distinct or sometimes confluent; 

 microspores 0.028 to 0.034 rnrn- long, dark brown, papillose. — Bot. Ga- 

 zette, 1878, p. I. 



Var. IMMACULATA. Larger, leaves sometimes as many as 60, 6 to 9 

 inches long; sporangium without spots ; macrospores rather smaller, 0.40 

 to 0.56 mm. in diam.; microspores 0.029 to 0.031 mm. long, spinulose. 



In the saline flats (called alkali flats, but impregnated with sulphates) 

 of the Indian Territory, near Limestone Gap, between Arkansas and Red 

 livers, associated with the few coarse plants which can live in those local- 

 ities overflowed in winter and spring, and baked hard in summer and 

 autumn, such as Iva angustifolia. Ambrosia psilostachya., Arenaria 

 Pitckeri, and with Jsoetes tnelanopoda, but in rather drier localities than 

 this; maturing in May and June, G. D. Butler. The variety near Nash- 

 ville, Tenn., in cedar barrens, in damp places on the limestone flats, with 

 Leave7nvorthia, Talhium, Sediim pidchellum, Schcenolirio7i, several Junci, 

 etc., A. Gattinger. — This species, also peculiar to the Mississippi Valley, 

 is quite unique in this genus by its dioicity, though its nearest ally, the 

 last mentioned one, approaches it. From this it is readily distinguished 

 by the absence of the velum, by the deep brown color of the microspores 

 and the larger size of the macrospores ; in these last I notice the peculi- 

 arity that the ridges themselves which separate the faces of the spores are 

 also more or less tuberculated, while in other species they are quite 



smooth. 



* * Velum complete. 



14. I. NuTTALLii, A. Braun in Herb. Similar to the last two species, 

 with an almost globose slightly grooved trunk and 20 to 60 slender bright 

 green leaves,'3 to 9 inches long, with only 3 peripheral bast-bundles; spo- 



