Holm. — Bartonia , Muehl. An Anatomical Study. 447 
In comparing these two species with each other, we notice the following 
anatomical characters, by which they may be distinguished : 
Root without exodermis, B. verna. 
„ with thick-walled „ B. lanceolata. 
Stem without sheath of mestome-parenchyma, B. verna. 
„ with „ ,, thick-walled „ B. lanceolata. 
Leaf with wrinkled cuticle and very open chlorenchyma, B. verna. 
„ „ smooth „ „ compact „ B. lanceolata. 
Our genus has thus several histological features in common with 
Obolaria (1. c.), and we notice especially the root-structure, that of a 
typical mycorhiza, common to both. Moreover, the stem of Obolaria 
possesses also an endodermis, and shows, like Bartonia , the complete 
absence of stereome ; the mestome-strands are also bicollateral. But the 
foliage of Obolaria is better developed, the leaves being larger and quite 
fleshy ; nevertheless the structure is much the same, the chlorenchyma 
being only represented by a homogeneous tissue of roundish cells with no 
indications whatever of palisade-cells. In regard to the floral structure, the 
corolla of Obolaria shows the presence of nectaries, which do not occur in 
any of the species of Bartonia. 
The fact that the roots are mycorhizae might indicate that these genera, 
Barto7iia and Obolaria , are saprophytic, but the presence of no small 
amount of chlorophyll in stems, leaves, and ovaries excludes them from 
the Holosaprophytes ; they may, however, be regarded as Hemisapro- 
phytes. Bartonia and Obolaria are near allies so far as concerns the 
imbricated corolla-lobes and the ovules covering the inner face of the 
carpels ; but the presence of nectaries in the corolla of Obolaria , besides 
the calyx with only two leaves, which resemble bracts, make the genus 
very distinct from Bartonia. Whether these distinctions may prove 
sufficient for the removal of Obolaria from the Erythraeinae we must 
leave to the judgement of future monographers of the family. In the 
present paper we wished only to describe the structural peculiarities as a 
contribution to the knowledge of these peculiar and interesting plants, 
which, so far, have been only imperfectly known. 
