ANATOMICAL STRUCTURE OF THE OLIVE 



(OLEA EUROPEA)." 



By Dr. Theo. Holm. 



Fig. 11.— Transverse section of a young 

 lateral root of the third order of an olive 

 tree from Palm Springs, Cal., showing 

 a hairy epidermis(Ep.) and cortex(C.). 



ROOT STRUCTURE OF THE OLIVE. 



Characteristic of the root structure of the genus Olea is the presence 

 of stereome on the inner face of the pericambium and the prevalence 

 of cambial cell divisions on the inner face 

 of the leptome. Otherwise, the arrange- 

 ment and development of the various tis- 

 sues is not different from that of many 

 other dicotyledons. 



The structure is as follows: In the 

 young lateral roots of the third order (figs. 

 11 and 12) the epidermis (Ep.) is very 

 hairy and covers an exodermis (Ex.) of 

 thin-walled cells in a single layer; this 

 exodermis is not contractile. The cortex 

 (C.) is compact and thin walled; it con- 

 sists of eight layers, more or less filled 

 with starch; a thin-walled endodermis (End.) is plainly visible, bor- 

 dering on the pericambium (P.) which shows isolated strands of 

 St. stereome (St.) outside the leptome. The 



stele is tetrarch, there being four strands of 

 leptome (L.) alternating with four rays of 

 hadrome (H.), which extend to the center 

 of the stele. Increase in thickness begins 

 even in these thin roots, since cambial 

 (Camb.) divisions are noticeable on the inner 

 face of the leptome, although the increase 

 does not extend beyond the formation of 

 these few layers. 



In lateral roots of the first or second order, on the other hand, the 

 increase in thickness attains mucli larger dimensions, due to the 



a This description of the anatomy of olive roots, leaves, and stems, with ten illus- 

 trations, was prepared at the writer's request by Dr. Theo. Holm, of Brookland, 

 D. C, from material collected from several California groves. 



57054°— Bui. 192 11 4 47 



Fig. 12.— Inner i)ortion of the same 

 transverse section of the olive root 

 shown in figure 11, (X210.) 



