 The <unk> formed between several Suillus species and Aleppo pine has been studied under in vitro conditions in the laboratory . Tree shoots inoculated with either S. collinitus , S. bellinii , and S. mediterraneensis tended to grow better and showed superior mycorrhizal development than other tested Suillus species , suggesting that the three have a " physiological specificity " for the tree . A 2010 publication reported that the fungal hyphae are covered in crystals of oxalic acid , which , in addition to reducing soil pH , reduces grazing by the soil <unk> <unk> candida . 
