1888. | BOTANICAL GAZETTE. 93 
Pringle in Mexico, and Macoun in Vancouver Island. His 
second prophecy, that ‘* some of the apparently local species 
will yet be found in a more extended area,” depends largely — 
on the activity of collectors in the field. 
Some general conclusions may be drawn from the above 
notes on geographic distribution : ; 
1. The genus Isoetes has‘a world-wide distribution, be- 
ing represented not only on every continent, but in almost 
every part of every continent. 
ile the range of the genus is world-wide, the range _ 
of most of the species is remarkably narrow. Excepting the 
two boreal species, I. lacustris and I. echinospora, and the 
three Mediterranean species, I. velata, I. hystrix and I, Du- — 
rizi, the remaining species are largely local, many being 
known from a single locality. care es 
. France for Europe and Massachusetts for America 
present the largest number of species and varieties, Owing, 
doubtless, to the fact that their collectors have been more 
active and watchful for these inconspicuous plants. “ies 
4. No center of distribution seems apparent; we are- 
unable to assign headquarters for the genus. 4 : 
. As we approach tropical regions from both north and 
south we find a decrease of aquatic and subaquatic forms | 
and a corresponding growth of amphibious, pseudo-terres- 
trial and terrestrial forms. 3 ed a 
Probabilities derived from a study of distribution 
point not only toward a much wider range for individu es 
species, but also to the discovery of many more species aS 
collectors turn their attention to them. ea 
true of numerous other aquatic plants, water- — 
fowl have doubtless been responsible for the wide distri NS, 
tion of certain species, notably I. lacustris and I. echinospora, 
which, no doubt, encircle the northern hemisphere. Rare. 
We add the descriptions of two new species: ey 
Isoetes Mexicana. Amphibious : rootstock two-lobed: leaves 
right green, 12-22 cm. long; stomata numerous: 
sporangia oval, 5 mm. long, 3 mm. wide, delicate, unspotted 5 _ ; 
; 
asl 
t : 
verging ridges in strong relief: microspores slate-colored, ~ 
0.028-0.033 mm. thick, mostly smooth. ca 
quetraandi. = 
It should be noted that the two apparent exceptions to this law, I. trique cine 
Lechleri, though found in equatorial regions, are both high mountain forms. ce 
; 
