30 EQUISETITES. 
Tubers of Equisetum and Equisetites—In Duval-Jouve’s Mono- 
graph on the French species of Eyuisetum some good figures are 
given, which have been repeatedly reproduced by subsequent 
writers, showing the nature and manner of occurrence of tubers. 
On pl. i. fig. 4,' is represented a node of a rhizome of Eyucsetum 
maximum, Lam., from which three sets of pyriform tubers are 
given off; fig. 1 of the same plate shows elliptical tubers attached 
to a rhizome of Z. arvense, L., and in fig. 5 the tuberous branches 
of LH. palustre, L. These tubers occur either singly, or several 
together, in the form of a string of beads, and are simply inter- 
nodes of rhizome branches which have been specially modified to 
serve as reservoirs of food material. The internal tissues have 
increased enormously in bulk, and, at the expense of growth in 
length, the internodes have become tuberous, with their parenchy- 
matous cells rich in starch. At the base of each tuber the dentate 
leaf-sheath is easily seen, and if the end tuber of a chain be 
removed the sheath remains attached to the tuberous internode 
next below in the form of an apical crown. Frequently the tubers 
are wrinkled on the outside, and, where an axial cavity is present, 
this surface-wrinkling may be very pronounced. These special 
internodal structures, after passing through a period of rest, are 
able to grow into new Lguisetum plants, and thus serve the purpose 
of vegetative reproduction. 
Among recent “‘ Horsetails ”” they occur more or less frequently 
in such species as LE. arvense, L., E. sylvaticum, L., EL. Telmateda, 
Ehrh., etc. According to Duval-Jouve, Hyguisetum tubers were first 
noticed by Helwing in 1712, and are thus described by him in 
E. arvense:*—“* Hus radicibus glandes copiose adherent, et quam 
maxime in agris arenosis effodiuntur a sucbus et pueris rusticis. 
Grati et dulcis sunt saporis. Instinctu nature sues odoratu super- 
ficiem terre detegunt, et tam diu terram evolvunt, quoad appro- 
pinguent ad glandes, Polonice Geguzie, nostratibus ‘ Hrd-Niisse? 
dictos, quod subulet animadvertentes statim accurrunt, et pedibus 
porcos abigentes leviosimo labore nucleos suos terrestres colligunt. 
Maturescunt circa tempora autumni.” 
In 1768 Alberti V. Haller briefly refers to the same bodies as 
1 Hist. Nat. Equisetum. 
® Helwing, Fl. Plant. indig. Pruss. p. 31. 
