TH E systems of organs of which a higher plant more especially is composed generally hold an intimate physical relation to one another. They are bound together so intimately by reason of their position in root or shoot that the growth, development or response to stimulus of one is in a very great measure molded by the growth, development or reaction of all the rest. In addition to these considerations, when the origin of tissues or of organs is being investigated, account must also be taken of the nutrition of the special organ as well as its especial relation to environment external to the plant of which it is an integral part. Thus the complex physical interrelations, and the physiological correlations as well, make the study of the functions, and behavior of the individual tissue, or organ, as a possible independent unit one of great difficulty. These general facts probably hold for plant tissues as a whole, but one system, namely, the trichorial system, offers a favorable field in which to study the origin, development and biological relationships of plant organs, inasmuch as it is comparatively little affected by other tissue systems. Beyond growing out of epidermal cells, remaining permanently attached to the epidermis, and deriving nourishment from the subjacent cells, the trichormes lead an independent existence, and in origin, development and form are not directly influenced, as the other tissues are affected, by the pressure of enveloping tissues, and in certain plants, as Franseria dunmosa, the trichomes go one step further on the road to independence, in that they are chlorophyll-bearing and in a sense probably auto-trophic. For these and other 779