156 



towards the extremity. They spring from a tuber, which, in mature 

 plants, is about the size of a hazel-nut. This tuber seems analogous 

 to what I have called a tufted rhizoma in ferns : it is of various form, 

 commonly, however, slightly bilobed ; its external coating is spongy, 



and of a dark brown colour approaching to 

 black, and apparently composed of decayed 

 portions of its substance : the interior is 

 very compact and of a pure white, with a 

 small and nearly pellucid portion in the cen- 

 tre, whence the leaves appear to originate. 

 The taste of this tuber is earthy, but not 

 otherwise remarkable, and it seems perfectly 

 innoxious, as I have eaten several without 

 injury. A longitudinal section of the tu- 

 ber {t t) with its attached radicles, is shown 

 in the margin. Wahlenberg says that this 

 tuber vegetates in the interior while dying 

 round the circumference,* a mode of ac- 

 counting for its appearance which seems 

 highly probable. 



The leaves are sessile, and rise from the 

 crown of the tuber ; at the base they are 

 very broad, and furnished with membranous 

 margins, which clasp the inner leaves much 

 in the same manner as the scales of a hly- 

 bulb. With the exception of this basal 

 portion, the leaves are nearly cylindrical, 

 sometimes however approaching to a quad- 

 rate form, with obtuse angles, and termi- 

 nating in a sharp point ; they are hollow, 

 the interior being divided by longitudinal 

 septa into four tubes, which are again sub- 

 divided into numerous compartments by 

 transverse septa placed at irregular distan- 

 ces : these transverse septa are very apparent through the semi-pellu- 

 cid substance of the leaf, and give it a jointed appearance. The 

 leaves are extremely brittle, and usually break at these apparent joints. 

 They are persistent, — the plant being in every respect an evergreen, 

 whence the Linnean name of IsoeteSy\ signifying that its appearance 



* Flora Lapponica, 294. 



t /croj aequalis, zto^ annus. 



