Assimilation Research Articles

The Puerto Ricans: Protest or Submission?

The situation of Puerto Ricans in the United States cannot be seen as abstracted from that of those living in Puerto Rico. Puerto Rico has been a colony of the United States since 1898, and the most pervasive characteristic of its population—both in the Island and in the Mainland—is its colonialist mentality or world view: hence, the attitude of sub mission and acquiescence characteristic of the Puerto Ricans. The only forces in Puerto Rico that represent Puerto Rican pro test against the perpetuation of colonialism in Puerto Rico are the proindependence groups. In this respect, their goal is simi lar to that of the Black Power advocates in the United States, because both groups are faced with a similar situation. Only when Puerto Ricans have achieved decolonization, both psycho logically and politically, will they be able to come of age as a true protest movement. Otherwise they run the risk of a total destruction of Puerto Rican nationality, and cultural assimila tion by the United States.

Studies on the Expansion of the Leaf Surface

SUMMARY An investigation was made of the expansion of the leaf surface of cucumber at temperatures of 12o, 18°, 24o, and 30o C. with two levels of visible radiation (40 and 80 cal. cm.-2 day-1). The relative rate of expansion of the leaf surface increased with temperature up to 24o but was lower at 30o than at 24o. It was slightly greater with the higher than the lower level of radiation at the lower temperatures only. This rate was the resultant of the rate of unfolding of new leaves and the rate of expansion of the component leaves. The rate of leaf pro duction increased with increasing temperature up to 240 and was constant there- , after, but leaves unfolded from the terminal bud more rapidly with increase in temperature over the entire range. The rate of expansion of individual leaves was greatest at 240, being less at both lower and higher temperatures. Differences in this rate between temperatures increased in the order: cotyledon, leaf 1, leaf 2. Leaf production and unfolding was greater with the higher level of radiation but the expansion of individual leaves was not influenced. These results suggested the following interpretation of the expansion of the leaf surface. Its potential rate is set by the rate of unfolding of leaves from the terminal bud, which depends mainly on the temperature and the rate of assimila tion by the upper leaves and the terminal bud, the demand for assimilate exceed ing the supply in this region. The demand for mineral substrates by the terminal bud is low and not influenced by a wide variation in potential supply. After un folding from the terminal bud, the leaf provides most of its own supply of carbo hydrate by assimilation and this can be met at a low level of radiation. Surplus assimilate is diverted to the roots and stems which respond much more to in creased radiation than does the leaf surface. The demand for mineral substrates by expanding leaves, however, is high—the greater the number expanding at any time the more likely is the demand by any one leaf to exceed the supply. This leads to a reduction in the number of cell divisions and, consequently, a reduced rate of expansion and a smaller leaf. The optimum level of any environmental factor is that at which the most effective compromise between these conflicting processes is reached.