
18. BOTANICAL GAZETTE [JANUARY 
normal, its interruption abnormal. So far, botanists have not ven- 
tured to consider these two conditions as anything but specific 
characters, and if they were really constant they would certainly 
be of some importance; but my observations have lately shown 
that they are not to be depended upon as constant in all species. 
For example, in Carex jispidula3 the pericambium may be inter- 
rupted either by all the proto-hadrome vessels or by some of 
them, while in C. firma and C. supina this tissue is either con- 
tinuous or interrupted by the majority of these vessels. These 
variations were noticed in roots of a single individual, and it is 
very likely that such irregularities are much more common than 
is supposed, even in spite of an examination of abundant mate- 
rial. In regard to the Eriocaulacee, Van Tieghem describes the 
root-structure of a few species, and calls special attention to the 
very regular interruption of the pericambium by all the proto- 
hadrome vessels in #. decangulare, E. septangulare, E. Dregei, E. 
Sellowianum, and £. Paraguayense; while in £. atratum and E. 
Kunth only some of these vessels have broken through the 
pericambium. Moreover, this author attributes six or eight rays 
of hadrome to &. decangulare, and states that each ray is com- 
posed of two vessels, one bordering on endodermis, the other on 
the central vessel, but separated from it by a layer of conjunc- 
tive tissue. Besides Eriocaulon Van Tieghem has described 
Lachnocaulon,+* Paepalanthus, and Philodice. 
Having observed the irregular disposition of the proto- 
hadrome in some species of Carex, it seemed well to investigate 
the matter further, and I have examined the root structure of 
various other genera, and among them Eriocaulon; and since 
E. decangulare L.. exhibits a similar and even more striking varia- 
tion in its root structure, it was thought worth while to present 
3On a collection of Carices from Alaska, with remarks upon the affinities of 
-Carex circinata and C. leiocarpa C. A. Mey. Am. Jour. Sci. IV. 10:279. 1900. 
4 Judging from Van Tieghem’s description of the root structure in Lachnocaulon 
our North American Lachnocaulon Michauxii resembles that which Van ane has 
ascribed as sede to Paepalanthus, 

