The present invention relates to, inter alia, a novel crystalline free-plate habit or morphology, processes for preparing the crystalline free-plate habit, and uses of the crystalline free-plate habit of the L-arginine salt of (R)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-1,2,3,4-tetrahydrocyclo-penta[b]indol-3-yl)acetic acid (Compound 1) in the treatment of S1P1 receptor-associated disorders, for example, diseases and disorders mediated by lymphocytes, transplant rejection, autoimmune diseases and disorders, inflammatory diseases and disorders (e.g., acute and chronic inflammatory conditions), cancer, and conditions characterized by an underlying defect in the vascular integrity or that are associated with angiogenesis such as may be pathologic (e.g., as may occur in inflammation, tumor development, and atherosclerosis).