30 EQTriSETITES. 



Tubers of Equisetum and EquisetiUs. — In Duval-Jouve's Mono- 

 graph on the Prenoh species of Equisetum some good figures are 

 given, which have been repeatedly reproduced by subsequent 

 writers, showing the nature and manner of occurrence of tubers. 

 On pi. i. fig. 4,^ is represented a node of a rhizome of Equisetum 

 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 E. arvense, L., and in fig. 5 the tuberous branches 

 of E. 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 

 intemodal structures, after passing through a period of rest, are 

 able to grow into new Equisetum plants, and thus serve the purpose 

 of vegetative reproduction. 



Among recent " Horsetails " they occur more or less frequently 

 in such species as E. arvense, L., E. sylvaticum, L., E. Telmateia, 

 Ehrh., etc. According to Duval-Jouve, Equisetum tubers were first 

 noticed by Helwing in 1712, and are thus described by him in 

 E. arvense:'' — "Sujus radicihus glandes copiose adhmrent, et quam 

 maxime in agris arenosis effodiuntur a suibus et pueris rustieis. 

 Grati et dulois sunt saporis. Instinctu natures sues odoratu super- 

 fioiem terrcB detegunt, et tarn diu terram evolvunt, quoad appro- 

 pinquent ad glandes, Polonice Geguzie, nostratibus ' Erd-Nilsse' 

 dictos, quod subulci animadvertentes statim aceurrunt, et pedibus 

 porcos abigentes leviosimo labore nuchas suos terrestres coUigunt. 

 Maturescunt circa tempora autumni." 



In 1768 Alberti Y. Haller briefly refers to the same bodies as 



' Hist. Nat. Equisetum. 



* Helwing, Fl. Plant, indig. Pruss. p. 31. 



