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Scott Shapiro offers an elaboration and defense of “legal positivism,” in whichthe official acceptance of a planfigures as the central explanatory notion. Rich in both ambition and insight,Legalitycasts an edifying new light on the structure of positive law and its officialdom. As a defense of positivism, however, it exhibits the odd feature that its main claims will prove quite acceptable to the natural lawyer. Perhaps this betokens – what many have begun to suspect anyway – that our usual tests for classifying legal theories (as positivist or not) are, in the present state of discussion, no longer credible. In any case, my hope in the following remarks is to suggest how certain ambiguities inLegalitymight easily be resolved in favor of PlanningNatural Law. The Planning Theory of Law, in other words, is not proprietary to positivism.

A greenhouse experiment used a replacement series design to compare the vegetative growth 6 wk after emergence in pure cultures and mixtures of winter wheat and Italian ryegrass, with phosphorus (P) levels recommended by soil testing. The planting proportions of wheat and Italian ryegrass were 100 and 0%, 75 and 25%, 50 and 50%, 25 and 75%, and 0 and 100%, respectively. There was no alleopathic interaction between the species. Both species in all pure and mixed cultures had substantially less growth in the low-P than in the recommended P treatment. However, the relative performance of the two species differed between P treatments. In the recommended P treatment in pure culture, Italian ryegrass had more tillers and greater root weight and length than wheat. Pure culture wheat in the low-P treatment exceeded pure culture Italian ryegrass in leaf area, weights of leaves, stems, and roots, and root length. Thus, the growth of wheat was inhibited less by P deficiency than the growth of Italian ryegra...

A greenhouse experiment compared the vegetative growth in pure cultures and mixtures of winterTriticum aestivumcultivar ‘Mit’ andLolium multiflorumcultivar ‘Marshall’ in continuously watered controls and drought treatments. ControlL. multiflorumin pure culture 14 wk after planting produced more leaf area, tillers, and dry weights of stem and root than controlT. aestivumin pure culture. The greater seed size, larger initial leaf area, and height allowedT. aestivumto produce greater final leaf area and dry stem weight in control mixtures thanL. multiflorum.Watering following drought shifted the relative performance of the two species in pure cultures and mixtures compared to controls. The ability ofT. aestivumto maintain a greater leaf expansion rate during drought and a greater leaf area afterward thanL, multiflorumallowedT. aestivumto attain greater growth thanL. multiflorumin pure cultures exposed to temporary drought followed by watering. Conversely, drought and its relief enhanced the relative competitiveness ofL. multiflorumcompared to controls in mixtures withT. aestivum.During 4 wk of watering following the drought,L. multiflorumin mixtures grew vigorously and was similar toT. aestivumin all measures except in height and dry stem weight. Thus,L. multiflorumwas similar in root growth withT. aestivumin control and drought mixtures and had its aboveground competitiveness amplified by the cycle of drought and watering in this study. There was no evidence of an allelopathic interaction between the two species.

Greenhouse experiments in central Texas assessed the relative importance of above- and belowground interactions of semidwarf Mit wheat and Marshall ryegrass during vegetative growth. One experiment used partitions to compare the effect of no (controls), aboveground only, belowground only, and full interaction for 75 d after planting (DAP) one wheat and nine ryegrass plants in soil volumes of 90, 950, and 3,800 ml. The results with the different soil volumes were similar. Wheat growth in the aboveground interaction only did not differ from controls. However, the full or belowground only interaction of wheat with ryegrass reduced wheat height, leaf number, tillering, leaf area, percent total nonstructural carbohydrates in shoot, and dry weights of leaves, stems, and roots 45 and 75 DAP compared to controls. Wheat in full and belowground interaction only did not differ from one another in growth. A replacement series experiment of 56 d also showed that the competitive advantage of ryegrass was relatively greater in root than in shoot growth. No allelopathic response of wheat to ryegrass occurred. While the tallness of the semidwarf wheat minimized aboveground interference by ryegrass, the root growth of the thinner and more fibrous roots of ryegrass greatly enhanced its belowground competitiveness.