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We explore the conditions under which LARGE aluminum enhancements might be produced by very deep mixing and proton capture nucleosynthesis in bright globular cluster giants. We find that: (1) The initial abundances of neutron rich magnesium seed nuclei must be surprisingly large for old metal-poor stars; [Al/Fe] overabundances near 1.0 dex require that the initial $^{25}$Mg/$^{24}$Mg and $^{26}$Mg/$^{24}$Mg ratios must be approximately twice as large as they are in the sun (assuming that the $^{25}$Mg/$^{26}$Mg ratio is approximately solar). (2) Cluster giants with large aluminum enhancements ($\sim$1.0 dex) produced by very deep mixing should show smaller but observable Mg depletions ($\sim$0.2 dex) as a result of the destruction of $^{25,26}$Mg. (3) Large aluminum enhancements are very likely to be accompanied by significant hydrogen depletions and helium enhancements throughout the stellar envelope. Adding hydrogen from the envelope to the hydrogen burning shell may have an observable impact on giant branch evolution; a helium enriched envelope will surely have an important impact on the star's later location on the horizontal branch.
