A mature trichome is twenty to forty times the size of the epidermal cell from which it arises. All parts of the cell show a correlative increase in size. The nucleolus may become several times the size of the unmodified epidermal nucleus. The pro-chromo-somes, the permanent bodies of the nuclear picture, often become as large or surpass the size of the nucleus of their origin. The original homogeneity of the pro-chromosomal material is retained in the exaggerated ones and there can be no question of division of the chromomeres to account for their increase in size. Increase in size is due to a distension of constituent parts. Living nuclei show no organization save for the nucleolus. Severe mechanical handling and treatment with aceto-carmine crystallize out a nuclear organization otherwise invisible. Therefore fixed and stained material showing nuclear organization arouse the suspicion of artefact. Trichomes may be classified with glandular structures in insects and may be placed in the category of physiological manifestations seen in. the salivary glands of some dipteran larvae. The organization of the germ cells of Mercurialis annua. cannot be deduced from the enlarged nucleus of the trichome. On the contrary the new function assumed by the developing trichome seems to impress itself an the whole cell and its form becomes a visible to the eye expression of forces that cannot be evaluated in terms of the visible. The nucleus of the trichome can no longer be regarded as a directing agency of the cell but it has become a passive organ caught in the current of function. It is buffeted about at will and becomes misshapen and distorted by forces which it may have previously controlled.