LECT. IV.] THE ROOT. TUBERS. 149 



other. They comprehend the following species, 

 regarding them as appendages of the root : 



1. The Conjoined ovate tuber (Tuber conjunc- 

 tum ovatum) is an egg-shaped tuber, in immediate 

 contact with another, and more rarely a third, at 



the point of its attach- 

 ment to the stem of the 

 plant, as in the Orchis 

 tribe (fig. q). When there 

 are three 'tubers, one of 

 them is generally shrivelled 

 almost to a skin, another 

 a little less so, and the 

 third quite plump: and when there are two only, 

 one is always somewhat shrivelled, if the root be 

 examined after the plant has flowered. The full 

 tuber is the formation of the present year, and 

 bears on it a gem for the production of the plant 

 of the following year ; but> the shrivelled one is 

 that of the preceding year, which having its nu- 

 tritious contents exhausted in formation of the 

 herb and the flowers, shrivels towards autumn ; 

 and either withers away altogether and disappears 

 in the succeeding winter, or remains a mere ske- 

 leton in the third year. The ovate conjoined tuber 

 is therefore biennial, being formed and perfected 

 in one year, and performing its functions and dy- 

 ing in the second. In fig. q are seen these three 

 states of tuber as displayed in Orchis acuminatum: 



L3 



