320 BOTANICAL GAZETTE [NOVEMBER 
3. The pectic material in most of the cases at first is in the form 
of calcium pectate or pectose; pectic acid could not be detected 
with certainty. The pectic layer is somewhat thicker in loam than 
in sand." 
4. The root hairs are somewhat acid in the forms studied, and 
there is a tendency to be slightly more acid in loam than in sand. 
5. Whether the acidity of the root hair can be ascribed to the 
presence of pectic material or to some other cause has not been yet 
determined with certainty. 
Acknowledgement i is due to Dr. SopH1a H. EcKxerson for her 
suggestions and criticism during the progress of this study. 
East Orance, N.J. 
s 
LITERATURE CITED 
1. Mancry, M. L., Sur la constitution de la membrane de vegetaux. Compt. 
Rend. 107:144-146. 1888. 
, Etude historique et critique sur la presence des grey pectiques 
dans les tissues des vegetaux. Jour. Botanique 6:12-10. 
3. OvEn, S., Ziir Frage der Aciditat der Zellmembranen. ber Denti: Bot. 
Gesells. 34:648-660. 1916; Review in Bot. Centralbl. 137:103. 1918. 
4. Roserts, Epitx A., Epidermal cells of roots. Bort. GAz. 62:488-505. 1916. 
5. Sampson, H. C., Abscission in the Coleus leaf. Bot. GAz. 66:32-53- 1918. 
6. SKENE, M., The acidity of peli and its relation to chalk and mineral 
salts. Ann. Botany 29:65-87. 1 
7. Truoe, E., vee acidity: its hati to growth of plants. Soil Science 
5:169-193. I 
8. WIELER, A., Die Aciditaét der Zellmembranen. Ber. Deutsch Bot. Gesells. 
30: 304-406. 1912. 
2. 
* The pectose is usually changed to pectic acid by the hydrochloric acid. 
