LEAVITT: TRICHOMES OF ROOT. 
301 
and agree with the above in essential respects: JV. amazonum var. 
bl-anda, JV. coerulea, N. gracilis, JV. rubra, JV. scutellata, JV. SmitJi- 
eana. JVelumbium speciosum., as I found it, had neither root hairs 
nor trichoblasts. JBrasenia peltata, Cabornba caroliniana, and 
Nuphar advena (pi. 19, fig. 102) are much like Nymphaea. 
Transfusion Cells of the Exoderm. 
In the hypodermal layer, or exoderm of the root of many plants 
an alternation, in each longitudinal row, of elongated prismatic 
elements and short roundish or oval cells has been noted by several 
investigators. 1 As regards origin, form, and probable function, as 
well as distribution in Angiosperms, the short cells are related in an 
interesting way to the short trichomic elements of the epidermis 
already described. Several typical examples, which I have studied, 
may be briefly described. 
Eucliaris amazonica. — The alternation of long and short cells is 
established in the young exoderm, very near the growing point, by 
the unequal and slightly oblique division of the cells (pi. 19, fig. 
103). The segmenting walls incline slightly toward the root apex 
as they run outward to the epidermis. The fundaments of the 
transfusion cells are therefore truncate wedge-shaped, the broader 
base outward. They are cut from the proximal end of the mother 
cells. Immediately afterwards they appear in the living state 
appreciably darker than the longer segments. As the layer matures, 
the smaller cells become rounded, as viewed tangentially. In 
radial longisection the general wedge-form is preserved. The outer 
face becomes strongly convex, and at the same time the adjacent 
long cells become curved in such a way as to elevate the short cells, 
which often protrude in a marked manner (pi. 19, fig. 104). The 
epidermis is thrown up into prominences. Its cells are sometimes 
separated above the protruding transfusion cells, which then have 
direct communication with the exterior. The transfusion cells often 
1 Ouclemans : Ueber den sitz del’ oberhaut bei den luftwurzeln der orchideen. 
Verb. d. kon. akad. d. wetensch., Amsterdam, math, pliys. klasse, 9 (1861). 
Leitgeb : Die luftwnrzeln der orchideen. Denkschr. d.akad. d. wiss., Wien, 
math, naturw. cl., 24 (1864). 
Juel: Beitrage zur kenntniss der liautgewebe der wurzeln. Ivongl. svenska 
vetenskaps-akad., Stockholm, Bihang t. liandlingar, 9 , no. 9 (1884). 
