LECT. IV.] THE ROOT. TUBERS. 159 



to the tribe of plants named Monocotyledons and 

 that .denominated Dicotyledons; it demonstrates 

 also, that the organization of the tuber has the 

 closest affinity to that of the stems of the tribe to 

 which it belongs. Thus, for example, the stem of the 

 Orchis mascula, which is an annual, tuberiferous, 

 monocotyledonous plant, consists of a lax cellular 

 texture enclosed in a cutis vera and epidermis, with 

 threadlike bundles of vessels running longitudi- 

 nally through it, at equal distances. The same 

 appearance is evident in the tuber, the vascular 

 bundles or cords being larger only, and inosculating 

 with each other at the lower extremity of the tu- 

 ber, whilst at the upper they pass into a transverse 

 bundle, which seems to unite with one cord of 

 vessels descending from the stem of the plant, and 

 two cords which apparently connect the vascular 

 system of the new tuber with that of the parent 

 stem and the old tuber. This organization is quite 

 obvious to the naked eye in the half-decayed tuber, 

 and can be made so in the new tuber if the stem 

 of the plant be cut transversely through about an 

 inch from the tubers, and the portion to which they 

 are attached inverted, and allowed to remain for 

 twenty-four hours in a decoction of Brazil wood. 

 When the vessels are thus filled with colouring 

 matter, a longitudinal section of the new tuber dis- 

 plays the vessels running in cords through the cel- 

 lular texture, which is now swelled with nutritious 

 fluids (vide plate 1. fig. 1. a), whilst a transverse 



