Here is the underside of a spider plant (Chlorophytum comosum) leaf. The straight structures appear to be vascular, and the dots we think are pores. These plants conserve water by opening their pores to breath only at night. According to NASA, spider plants also clean the air by removing volatile organic compounds like formaldehyde, benzene, and trichloroethylene. The distance between adjacent straight structures is about 1.7 mm.
Equipment used: Canon EOS Rebel T5i with 49 mm long extension tube.