5 



Montezumas of America, placed beside Duriaei or hystrix of 

 Europe, could not be separated by superficial examination, this one 

 point aside ; and some forms of Duriaei and hystrix, those growing 

 in damp places, habitually have no scales. On the other hand, the 

 three species mentioned can be separated at a glance from melano- 

 poda, Mexicana, or Pringlei. Leaf sections also are identical in 

 the Terrestres, the leaves being short, setaceous, with very small 

 cavities, and correspondingly wide dissepiments, and with four 

 stout bast-bundles (three in Nuttallii}, while the others named, as 

 well as most European, African, and Asian species which I have 

 examined, have stout leaves, four primary, and several accessory 

 bast-bundles, narrower dissepiments, and correspondingly larger 

 cavities. I leave a further discussion of these points for a future 

 occasion, especially as they bear only remotely on the immediate 

 subject in hand. I would remark, however, that Engelmann is at 

 variance, and I think rightly so, with European authors in his con- 

 ception of the subdivisions. 



Probably the main reason that our species of Isoetes are not 

 better known, both in habit and distribution, is the difficulty novices 

 experience in finding them. Their unattractive appearance and the 

 tedious process of analysis by use of a compound microscope, re- 

 quired to determine them with accuracy, have also conspired to 

 prevent general study. No character given can be expected to be 

 true in all phases. The leaves are long or short, according to the 

 stage of the water ; they are stout or slender, and the trunk large 

 or small, to correspond to the general vigor of the plant. The 

 outer sporanges are usually nearly round, while the inner are two to 

 four times as long as broad. The velum varies greatly in some 

 species, in certain forms of echinospora varying from ^-% indusi- 

 ate, and I have seen specimens from Maine and Amesbury, Mass. , 

 where a pin head would cover the opening. I should have consid- 

 ered this a good variety, had not fresh specimens from the same 

 place possessed a normal velum. The spores vary greatly in size, 

 and one may always expect to find some larger than the descrip- 

 tion allows. Location appears to regulate this. Juckermani, for 

 instance, is normal in this respect in most Massachusetts localities, 

 while New Hampshire and Maine plants usually measure 10-20 // 

 more. 



I know of no character more unreliable than the sculpture of 

 the spores. It is always easy to recognize Engelmanni in New 

 England, but southward even this breaks up into several varieties. 



