Emulsions made from petroleum distillates form, when stabilized with casein, oil-in-water emulsions if the oil is of less than 0.828 specific gravity. If the oil is of a greater specific gravity than 0.857 the emulsions are of the water-in-oil type. If the oil is of intermediate specific gravity (between 0.828 0.857) it either cannot be emulsified at all, or it forms a coarse unstable emulsion.The oil-in-water emulsions of light petroleum distillates are made more stable and the degree of the dispersion of the oil increased by the addition of NaOH, Ba(OH)2, Th(N03)4 and A12(S04)3• The water-in-oil emulsions of the heavier oils are reversed into the opposite type by the same four electrolytes.The effects of the above four electrolytes on emulsions of light and of heavy petroleum oils leads one to expect that these electrolytes will promote the emulsification of the unemulsifiable oils, which are of intermediate specific gravity (from 0.828 to 0.857), into oil-in-water systems. This is true in part. ExperimentalWhen either the hydroxide of Na or Ba is added to an unemulsifiable mixture of aqueous casein and an oil of intermediate specific gravity, the unstable system usually becomes first a water-in-oil emulsion, and then, on the addition of more of the same electrolyte, reverses into an oil-in-water emulsion. The following is a specific example of the production of a water-in-oil emulsion from an unemulsifiable petroleum oil, and the reversal of this emulsion into one of the opposite type on the further addition of the same hydroxide.Double reversal of petroleum oil emulsions.-A mixture of 25 c.c. of a petroleum distillate of 0.834 specific gravity and 25 c.c. of an aqueous casein dis-

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Certain plants are known to live vegetatively for many years, then flower and die. The most frequently cited example of this phenomenon is that of the century plant, A gave americana, which lives for a period of years without flowering, then sends up a tall, prominent inflorescence, and finally, after the maturing of the seeds, dies. This sexual periodicity is also characteristic of certain bamboos which blossom only after a cycle of years and then all simultaneously throughout an extensive region. The bamboos in the South Brazilian provinces of Santa Catharina and Rio Grande do Sul are said to blossom at intervals of about thirteen years, and Bambusa arundinacea on the west coast of Cisgangetic India blossoms at intervals of about thirty-two years (1). The complete and simultaneous dying off of the bamboos may in some communities prove disastrous by the wiping out of the chief available source of building material through the transformation of luxuriant bamboo forests into barren areas; or, it may prove of great economic value as a source of grain, especially when it comes, as it is said to (2), in times of drought and consequent famine.The length of the interval of years varies greatly in different bamboos.Bean (3) reports that ''Bambusa tesselata has been in cultivation for probably over sixty years, yet I have seen no record of its having flowered anywhere.'' In striking contrast with this is the case of Avrundinaria falcata var. glomerata which flowers almost every year on a certain number of culms. The latter is a case of partial or sporadic flowering as contrasted with the complete and simultaneous flowering which is the rule among bamboos. Intermediate types also exist. Bean (3) mentions the case of Arundinaria Simoni which flowered on odd culms in the bamboo garden at Kew for several years. He says, "'excepting that the flowering culms died, the plants were in no way affected. . . . They continued to flower in this Way every year up to 1903, by which time we had almost come to regard A. Simoni as a perennial. In that year, however, the plants flowered on every culm, and, after producing an abundance of seed, died. After that * Botanical Contribution from the Johns Hopkins University No. 62.