BOTANICAL GAZETTE. 



Vol. S. JANUARY, 1878. JVo. 1. 



The Species of Isoetes of the Indian Tepritory. — Isoetes melanopoda, J. 

 Gay, originally found in central and northern Illinois, then in the neiijhboring regions 

 of Iowa, seems to be peculiar to a belt of prairie country extending from northeast 

 to southwest, from Illinois to Iowa, the Indian Territory and Texas. Mr. E. Hall, who 

 discovered the species in Illinois, found it also some years ago in Dallas county, Texas, 

 and now Mr. G. D. Butler sends it from the Indian Territory. However the other char- 

 acters may vary, the microspores everywhere readily characterize the plant. They 

 are the smallest of any of our species, but varying in the same sporangium, between 0.25 

 and 0.35 mm., very rarely as much as 0.40 mm. in diameter, marked with confluent 

 knobs and curved and twisted (worm-like) low, sometimes almost indistinct, elevations, 

 visible, of course, only under a strong magnifier. The velum or membranaceous lold, 

 which more or less completely covers the spore case, or is, rarely, wanting, is in this 

 species usually narrow, or sometimes wider; in the southern forms it covers about one- 

 third oftlie upper half of the sporangium. Full-grown specimens are J^-l inch in diam- 

 ater at the almost black and shining base of the leaves; these, smaller and fewer in the 

 northern forms, are in the southern ones 30-50 in number and 8-12 inches in length, and, 

 as I iiave described them in Gray's Manual, triangular, with 4 peripherical fibrous bun- 

 dles and with numerous stomata. 



Isoetes Butleri, n. sp. — I name an allied species discovered by Mr. Butler, near 

 the latter, in drier soil, a much smaller plant with earlier (beginning of June) maturity. 

 It is at once recognized by its larger macrospores, 0.50-0.68 mm. in diameter, marked 

 wltii distinct knobs or warts, which rarely run together. The base of tlie plant is only 

 ^ inch thick, the slender leaves with dull whitish bases, only 8-12 in number, are 3-6 or 

 7 inches long, of exactly the same structure as those of the last species. Velum very 

 narrow or almost none. Microspores aculeolate in both, in the latter species a little 

 larger than in the former. 



The species of Isoetes are usually, as is well known, monoecious, the exterior spo- 

 rangia bearing female or macrospores, the interior, later developing ones, male or micro- 

 spores. But /. md'iiiopoda is oftener dloicious than monoecious. Mr. lUitler examined 

 hundreds of specimens and found about one-third monojcious and two-thirds dioecious, 

 and of these the male and tem-ale plants in about equal numbers. Of Isoetes Butleri he 

 never could find a monoecious plant; all the specimens which he found as well as those 

 which I examined, were dioecious, both sexes in about equal numbers. — G. Engelmann, 

 iSt. Louis, Nov. 1877. 



To the foregoing description by Dr. Engelmann I append some remarks in regard to 

 the locality in which tliese plants occur. Botli were found near Limestone Gap on the 

 Missouri, Kansas & Texas railroad, about 70 miles north and 100 miles west of the Texas 

 and Arkansas boundaries, near tiie divide between the Red and Arkansas rivers. The 

 surface of the country is very rougli, woods and prairies alternating and of about equal 

 extent. There is a clay underlying most of the countr_v. Many wells and si)rings run- 

 ning into or passing through tJiis clay are damaged or sometimes rendered unfit f(H' use 

 by the quantities of sulpluites of magnesia and soda entering into solution therefrom. 

 Occasionally this clay arises to the surface, forming low, ievel places, which are jiopu- 

 larly known as alkaline fiats, but which I call "sulphate flats," these sulphates 



320GS 



