— 8— 



variety of the latter. B. hiemale intermedium, aside from anat- 

 omy, could hardly be separated from laevigatum, and there appears 

 to be no good stopping place from variegatum through Funstoni 

 to ramosisimum. B. hiemale Schleicheri of Europe runs into 

 ramosisimum. The only species of which I have seen no inter- 

 grades is scirpoides, and this may be expected to run into varie- 

 gatum when thoroughly hunted up. Indeed the European varie- 

 gatum anceps has nearly the anatomy and size of scirpoides, and 

 I have seen scirpoides from Scandinavia nearly as stout as 

 variegatum from Russia. 



The characters of diagnostic value are the nature of the 

 sheaths, their teeth, the marks on the keels, whether in cross- 

 bands or two rows of tubercles, the forms the silex covering 

 take in the grooves, and the arrangement of the internal organs. 

 The nature of the rib markings and internal organs is best shown 

 by a cross-section. The stomata and general epidermal characters 

 are well shown by taking a slice of the stem, wetting it, scraping 

 off the parenchyma and then viewing by transmitted light. It 

 may also be prepared by placing on a pinch of chlorate of potash 

 and applying a drop of sulphuric acid, thus burning out all but 

 the mineral part, but care must be used, as the substance is ex- 

 plosive. As stated at the beginning of these articles this section 

 is sufficiently well characterized to be regarded as a genus. 

 Among all other groups of plants genera are founded on com- 

 paratively slight differences. It is probable, as suggested by Milde, 

 that the sub-genera represent two different stages in develop- 

 ment, the Hippochaetae being the more primitive form and the 

 Equiseta more highly specialized derivitives. 



The subgenus itself is subdivided into several sub-sections, 

 two of which are represented in our area. The first, consisting of 

 ramosissimum, Funstoni and laevigatum, are characterized by 

 mostly annual stems, long ampliated sheaths whose teeth in 

 falling leave persistent bases, by the branches, if any, developing 

 normally at the same time as the stem itself, and by having 

 the vallecular bast stouter than the carinal and separating the 

 green parenchyma. The other, represented by hiemale, robustum, 

 variegatum and scirpoides, has stems persistent three or four 

 years, sheaths little if any longer than broad, tight to the stem; 



