An equation of the form y = kx2 describing more precisely the species—area relation for plant species in smaller areas is proposed as a result of intensive examination of species presence in six stands of three undisturbed plant communities in the midwest. Each individual equation for each stand is based on a relatively small sample of 900 m2, but within such an area, the fit of observed data to the equations is very close. In these equations, in which y represents species numbers and x the area, k varies primarily according to species size, while the exponent z more truly reflects the species—richness of the community. Both of these constants may prove to be important measures of different community features. The equations fit rooted data more closely than covered, and it is suggested that the former type of information, being easier to obtain and probably more accurate, is preferable. Comparison of published species numbers for larger areas in floras show clearly that the above equation, so very accurate in the smaller areas actually sampled,does not hold for larger areas as the actual number of species drops far below what the equation predicts. An equation describing this relation for a communityover it entire range of area cannot be accurately constructed without considerable additional information on species numbers in larger areas. Such an equation will probably be sigmoid and more complex than the ones presented here. A method is described whereby one may objectively select an appropriate plot size for a given community based on its equation and not affected by the size of the sample from which the equation is derived. Such equations provide a useful means of comparing several floristic features as well as helping to assess historical aspects of plant communities.

-methyl-d-aspartate (NMDA)-type ionotropic glutamate receptors mediate excitatory neurotransmission in the central nervous system and are critically involved in brain function. NMDA receptors are also implicated in psychiatric and neurological disorders and have received considerable attention as therapeutic targets. In this regard, administration of d-cycloserine (DCS), which is a glycine site NMDA receptor agonist, can enhance extinction of conditioned fear responses. The intriguing behavioral effects of DCS have been linked to its unique pharmacological profile among NMDA receptor subtypes (GluN1/2A-D), in which DCS is a superagonist at GluN2C-containing receptors compared with glycine and a partial agonist at GluN2B-containing receptors. Here, we identify ()-2-amino-3-(4-(2-ethylphenyl)-1-indole-2-carboxamido)propanoic acid (AICP) as a glycine site agonist with unique GluN2-dependent differences in agonist efficacy at recombinant NMDA receptor subtypes. AICP is a full agonist at GluN1/2A (100% response compared with glycine), a partial agonist at GluN1/2B and GluN1/2D (10% and 27%, respectively), and a highly efficacious superagonist at GluN1/2C receptors (353%). Furthermore, AICP potencies are enhanced compared with DCS with EC values in the low nanomolar range (1.7 nM at GluN1/2C). We show that GluN1/2C superagonism of AICP and DCS is mediated by overlapping but distinct mechanisms and that AICP selectively enhances responses from recombinant GluN1/2C receptors in the presence of physiological glycine concentrations. This functional selectivity of AICP for GluN2C-containing NMDA receptors is more pronounced compared with DCS, suggesting that AICP can be a useful tool compound for uncovering the roles of GluN2C subunits in neuronal circuit function and in the development of new therapeutic strategies.

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