摘要：TWO SPECIES OF NYMPHOIDES GROW IN MEXICO, N. INDICA AND N. FALLAX. SINCE ONLY A FEW SPECIES IN THE GENUS HAVE BEEN ANATOMICALLY STUDIED, WE WORKED ON THE VEGETATIVE ANATOMY OF BOTH SPECIES AND N. FALLAX IS STUDIED FOR THE FIRST TIME. WE DESCRIBE THE ANATOMY OF BOTH, AS SEEN IN SLIDES OBTAINED THROUGH MICROTOME, BY FREE HAND AND TRANSPARENTATIONS. WE FOUND THE ROOT SURFACE COVERED BY SEVERAL EXODERMIS LAYERS WITH A MUCILAGINOUS SECRETION; THE PRIMARY CORTEX IS CONSTITUTED BY ROUNDED CELLS AND LACKS INTERCELLULAR SPACES IN N. FALLAX, WHEREAS N. INDICA HAS ONLY A FEW, THE CELLS CONTAIN ABUNDANT INULINE FOR STORAGE; THE VASCULAR SYSTEM IS COMPOSED FROM 9 TO 10 XYLEM STRANDS OF A POLYARCH XILEM, ALTERNATE WITH THE PHLOEM; IT HAS A WELL DEFINED ENDODERMIS. THE STEM HAS ABUNDANT AERENCHYMA AND ASTROSCLEREIDS. LEAVES HAVE ANOMOCYTIC STOMATA ON THE ADAXIAL SIDE, AND ABUNDANT HYDROPOTEN ON THE ABAXIAL; VENATION IS ACTINODROME FL AVELATED WITH THE TERMINAL PORTIONS MODIFIED TO WATER PORES; BRANCHED SCLERENCHYMA PRESENT AS IDIOBLASTS ARE COMMON. IN TRANSVERSE SECTION, THE LAMINA HAS A SIMPLE EPIDERMIS, A MESOPHYLL DIFFERENTIATED IN A PALISADE PARENCHYMA THREE TO FIVE LAYERS THICK, AND A SPONGY MESOPHYLL WITH LARGE ABUNDANT AIR CAVITIES IN THE ABAXIAL SIDE, ASTROSCLEREIDS ARE ABUNDANT. THE MUCILAGINOUS EXODERMIS HAD NOT PREVIOUSLY BEEN DESCRIBED, AND THE OXALATE CRYSTALS DESCRIBED BY OTHER AUTHORS WERE NOT FOUND.
