81 



in bursting almost invariably at the tip, and from microchemi- 

 cal studies, however, we may conclude, in general, that the ma- 

 terial at the tip differs with that along the sides of the hair. 

 The tip wall substance is probably amyloid in nature, the side 

 wall "alcium pectate, while real cellulose may be found at the 

 base of the hair. According to Ziegenspek, Hydrocharis again 

 reverses the picture by depositing the amyloid substance at the 

 base, but this is entirely in keeping with the idea concerning 

 the nature of the wall substance in the area of increase of wall 

 substance. 



CYTOPLASMIC CONTEXT OF ROOT HAIRS 



In very young root hairs the cytoplasm is very dense and 

 more or less homogeneous. As the hair elongates, vacuoles 

 appear, and most observers report an accompanying activity 

 of the cytoplasm resulting in streaming throughout the cell in 

 both main and cross currents. Within these lines of flow are 

 irregular fiocculent masses of material as well as spherical 

 "glistening bodies" of many different sizes. These latter 

 structures are highly refractive and very numerous in root hairs 

 which are produced in alkaline solutions. 



It was with this type of cell that Mr. Farr attempted to 

 study the eft'ects of simple nutrient solutions, with the hope of 

 being able to interpret the eft'ect of ions or of small groups of 

 ions upon the process of cell enlargement. 



One kind of plant, the very young seedlings of Georgia 

 Collards, has been used throughout the experiment. The rate 

 of growth of the aquatic root hairs has been tested in single 

 nutrient salt solutions. The necessity for calcium in the ex- 

 ternal medium determined the choice of calcium salts in the 

 different experiments performed: 



Distilled water 

 Ca(0H)2 

 CaCb 

 Ca(N03)2 



CaS04 

 Ca(H2PO,)2H2) 



Kisser first demonstrated the necessity for the presence 

 of calcium in root hair formation. After having failed to pro- 



