MISSISSII'I'I J: XPEKIMKXT STATITiX. 



21 



Fig, 8. — Nicotiana Tabacum 



X 



Nicotiana alata 



Nicotiana Tabacum, N. alata and Hybrid, 



HISTOLOGICAL CHAR-\r;TER5. 



Stem Strl'cture; The stems of X. alata and the hr/brid ha\"e a 

 much thinner eori^ey. than X. Tabacum, and Ic.^.s woody tissue. The 

 cortex is IOoom thiol-: in X. Tabacum, o2om thick in the hs'brid and 37,5m 

 in X. alata. The xylern is also much thicker in X, Tabacurn, being 

 2000m thick, while m the hybrid it h, 300m thick, and in X, alata it is 600m, 



The epidermal cells of the stem ^-ar}- considerably in the three 

 plant- tinder comparison; in X, Tabacurn they are 90m long, G2m wide 

 and 30m thick, v,-a]l- having a thickness nearly unifonn. In X, alata, 

 the epidermal cell:-, are about 70m long, 33m vcide, and 27m thick; thev 

 var-,- in size con;~iderably. In the hybrid, they are o7m long, 26m wide, 

 and 24m thick; they also \-ary consideraVjb,-, AIultipl}ing together the 

 abo-,-e dimensions, vce find that the X, Tabacum epidermal cells ha^-e 

 a volume of 167,400 cubicM, X, alata cells 62,370 ':ubieM, and the hs'brid 

 cells 35,568 cubiCM, the hybrid cells having a volume much less than the 

 corresponding cells of either parent. 



In X, Tabacurn, the first two or three layers of cells beneath the 

 epidermi-; are globular in shape, and are \-ery similar to other cortical 

 cells, except that they are more richly supplied with chloroplastids. 



