IN the plant kingdom, species often occupy space uniformly. Patches of grass, stands of trees, tend to stop abruptly at margins instead of straggling or petering out. A Scottish horticulturalist is studying why this is so, all over the world and among many species.It is as if a certain but hard-to-define coherence forms the life-support system of a collective of plants: Where the sustaining conditions exist, the group persists. In less than a fortnight, the 70-year-old Soviet system came to an abrupt end. The media and the Sovietologists are studying this margin. Mikhail Gorbachev's detainment by hard-line agents, Boris Yeltsin's defiance of the coup attempt, a rallying of the people and a few tanks around the Russian parliament building, Yeltsin's humiliation of Gorbachev and of the Communist Party are descriptive: They may be only the drama, the manner in which a more fundamental set of forces appears to us. The communist system can be said to have simply died. Some would argue that the communist system was but a 20th-century form of Russian czarist rule. We do not know much about Boris Yeltsin. We have seen Boris bully Mikhail. Will Yeltsin's role be chiefly that of a free-market revolutionary, leading to a renewed Russian hegemony over its neighbors? Russia, with its own flag and stripped of its smaller neighbors like the Baltics, will still be a superpower if it can find a new political coherence. Will Yeltsin be able to negotiate Russia's place among nation s? Social orders today do not need to be large political collectives. As electronic networking integrates the globe, smaller units can persist. Western Europe can afford to yield some measure of political power to the European Community, in return for a larger, more integrated labor, marketing, and communications field to do business in. An interesting generational gap is building in Western Europe between an older group who look chiefly to the United States for the shape of things to come, and a younger gr oup whose fascination is growing with things European. Similarly across the Atlantic, a North American continent consciousness is emerging, as Canada, the US, and Mexico evolve into a larger market unit. The Bush administration needn't worry about the future of the Baltic states of Estonia, Latvia, and Lithuania, as if a critical mass of size is essential to national survival. These countries have the workforces and histories that will enable them to engage the more prosperous economies nearby. They may have difficulty dealing with the Russian populations that have grown up in their midst. But they have been oriented to Germany, not to Russia, as the dominant economic power in their region, and this will resume. The collapse of the Soviet system might well enhance Berlin's position as the capital city of central Europe. But Berlin's hegemony may depend on how modern economic and communication networking will offset the tendency toward centralization. As to the other Soviet republics wanting independence: How effective will their political and economic leadership be? And for Russia, we cannot yet discount the impact of winter, of the great distances, and the country's own ethnic and cultural tensions repressed for so long after the Lenin gang's seizure of power early this century. For Russia to find a clear sense of its border, its margin, it will need a clear national idea to unify it. The US has such an idea. It is based on individual rights, religious and intellectual freedom, and an imagination fired by a sense of an endless frontier. Europe, having failed often since the Romans, is trying to establish a modern European order based on freer trade. Russian nationalism may be a powerful emotional force, and economic reforms may lead logically toward linking with the faster running West. Gorbachev is proving to be a transitional figure in Russian history - a remarkably vigorous and courageous one at that. But he was cast aside because he tried to hold on too long to the Communist Party's tatters. Unless Yeltsin proves to embody whatever empowers the Russian sense of identity, as a Washington or Churchill or de Gaulle did their respective nations in times of survival, he will be a transitory figure too.