Holm. — Bartonia , Muehl. An Anatomical Study. 443 
opposite, but very frequently not so ; in vigorous specimens of B. tenella 
and B . lanceolata they are often quite crowded and strictly opposite at the 
base of the stem. The root-system is poorly developed and only repre- 
sented by some few slender, secondary roots, there being no primary. 
The germination seems to be unknown. 
I11 regard to the internal structure our genus is very little known, and 
no mention has been made in Dr. Solereder’s comprehensive work on the 
Anatomy of Dicotyledons 1 . Nevertheless the structure has been touched 
upon, though very briefly, by W. Botticher 2 and E. Perrot 3 in their 
treatments of the Gentianaceae. These plants are, as a matter of fact, 
very difficult to study from dried and pressed material alone, and since the 
writer has been able to obtain fresh specimens of B. verna and B. lanceolata , 
we take the opportunity to present the following results of our anatomical 
investigation, concerning the vegetative organs. 
Bartonia verna, Muehl. 
The Roots. 
As stated above, the roots are mycorhizae ; they are somewhat fleshy, 
sparingly branched, and lack hairs ; they are not contractile. A thin-walled 
epidermis covers directly the cortical parenchyma, no exodermis being 
developed. The cortex consists of about six compact layers, in which 
fungal hyphae are very frequent. Endodermis is thin-walled, and shows the 
Casparyan spots very plainly. The thin-walled, continuous pericambium 
surrounds two groups of leptome, alternating with two rays of hadrome, 
and the narrow vessels extend to the centre of the root. Other roots were 
observed to be triarchic. 
The Stem. 
The basal internode is cylindric, glabrous and smooth. A thick, 
wrinkled cuticle covers the epidermis (Plate XXXIII, Fig. 11), of which the 
external and radial cell-walls show a very pronounced thickening ; some 
stomata were observed (Fig. 11), and they were level with the surrounding 
epidermis. Inside the epidermis is a cortical parenchyma of about nine 
layers of thin-walled cells with narrow but distinct intercellular spaces. 
The cells of the cortex contain a little chlorophyll and are of about the 
same size throughout, but only the innermost strata are arranged radially, 
although no endodermis was observed. The cortex borders thus directly 
on the mestome-strands, the structure of which is very irregular, there 
being about ten groups of leptome, but an almost continuous ring of had- 
rome, besides four leptomatic strands, located in the pith. The innermost 
1 Systematische Anatomie der Dicotyledonen, 1899. 
2 Beitr age zur vergleichenden Anatomie der Gentianaceen. Inaug. diss. Erlangen, 1895, p. 55. 
3 Anatomie comparee des Gentianacees. Thesis. Paris, 1899, p. 192. 
