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apical (distal) member of the pair of daughter cells is always smaller than the basal. It has denser protoplasmic contents and its walls tend to bulge outward slightly. At some distance back from the tip, when elongation has ceased, this cell produces a root hair. The other cell, which rarely may divide again, never produces a hair. In these genera, therefore, differentiation for this character occurs very early and the potencies of the cells are sharply limited almost from the beginning. In Chloris and Sporobolus, on the other hand, trichoblasts ordinarily do not appear, all the cells being essentially equal in size from the beginning and all being capable of producing root hairs. Some of the cells stain differently from others, and a differentiation of root hair cells may occasionally be observed before the hairs are formed. These plants evidently provide good material for a study of the factors controlling the differentiation of root hairs. Summary.-Materials and methods are described, by the use of which it is possible to observe and measure the multiplication and growth of cells in living root meristems. This technique has been applied to the problems of the location of new cell walls, of "sliding growth," and of the differentiation of cells which are to form root hairs.

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The purpose of the standard experimental interview is to obtain an adequate sample of the behavior of an individual that will predict with a high degree of accuracy how he or she will act in everyday life. In order to do this effectively, it has been necessary to create a pattern of interviewing that will yield consistent results no matter who conducts the interview. The fundamental importance of completely standardizing the interviewer's behavior accounts for the detail in which instructions are given for the conduct of the interview. The necessity for standardization became evident after a long series of experiments had been conducted whose purpose was to develop means of overcoming the wide variations in the results obtained from the same person by different interviewers. The fact that an individual reacts differently to different interviewers is hardly surprising, but its significance is insufficiently appreciated. It is the consequence (often unconscious) of the interviewer's own personality which creates a style of interviewing sympathetic to it, whatever theoretical constructs say as to technique. For even though a person may have learned one of the several techniques of interviewing commonly taught at the present time, it can easily be demonstrated that, even though the same words are used, he will not obtain the same results as another interviewer with a different personality.

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