THE AQUATIC QUILLWORTS. 229 



named Isoctcs liicroglypliica. It is described as haying 

 ten to twenty leaves t\vo or three inches long, which 

 arc recurved and somewhat blunt at the tip. The 

 sporangium is unspotted and about one third indusiate. 

 The megaspores are very characteristic, 

 being from 485^ to 590^ in diameter, 

 and marked, except near the equator, 

 with rather large wormlike ridges. The 

 body of the spore is quite smooth and 

 greyish in colour. The microspores 



are from 31 p to 44^ loner and are warty. 



Me 

 In outward appearance the plant has isoetts 



great resemblance to Isoetes Tuckennani, to which it is 

 no doubt closely related, though the spore characters are 

 distinctive. 



Isoetes Macouni. 



Isoetes Macouni is known to grow only on Atka Island, 

 off the coast of Alaska, from whence it was brought by 

 J. M. Macoun in 1891. The plants were found in a 

 pool on the side of an extinct volcano, and apparently 

 in such a position as to be always submerged. The 

 leaves are from five to twelve in number, 

 about two inches long, and quite stout. 

 The megaspores average about 450 /" in 

 diameter and are set with stout blunt 

 spinules usually about twice as long as 

 broad. The microspores are finely and 



Megaspore of A 



Isoetes Macouni. densely papillose and about 40 /' long. It 

 is possible that this is still another form of Isoctcs ccJiino- 

 spora. It has considerable resemblance to the variety 

 Flcttii, and the differences it presents may be due to its 

 habitat. 



