I, and i'm sure everyone else, would like to see a much broader catalog of real colour photos that clearly show the wide array of deficiencies that present themselves. I bought the latest edition of indoor horticulture in the hopes that it would have this. Sadly, it did not. Offering only illustrations of leaves. Nowhere do i recall seeing anything shown or said about stem purpling due to magnesium deficiency. I am not criticizing anything or anyone. Just on my wish list, and many others i'm sure.