_Medullary_, belonging to, or of the nature of, pith (_Medulla_); pithy. _Medullary Rays_, the silver-grain of wood, 140, 141. _Medullary Sheath_, a set of ducts just around the pith, 140. _Meiostemonous_, having fewer stamens than petals. _Membranaceous_ or _Membranous_, of the texture of membrane; thin and soft. _Meniscoid_, crescent-shaped. _Mericarp_, one carpel of the fruit of an Umbelliferous plant, 121. _Merismatic_, separating into parts by the formation of partitions across. _Merous_, from the Greek for part; used with numeral prefix to denote the number of pieces in a set or circle: as _Monomerous_, of only one, _Dimerous_, with two, _Trimerous_, with three parts (sepals, petals, stamens, &c.) in each circle. _Mesocarp_, the middle part of a pericarp, when that is distinguishable into three layers, 120. _Mesophlœum_, the middle or green bark. _Micropyle_, the closed orifice of the seed, 110, 126. _Microspore_, the smaller kind of spore when there are two kinds, 161. _Midrib_, the middle or main rib of a leaf, 50. _Milk-vessels_, 135. _Miniate_, vermilion-colored. _Mitriform_, mitre-shaped: in the form of a peaked cap, or one cleft at the top. _Moniliform_, necklace-shaped; a cylindrical body contracted at intervals. _Monocarpic_ (duration), flowering and seeding but once, 38. _Monochlamydeous_, having only one floral envelope. _Monocotyledonous_ (embryo), with only one cotyledon, 24. _Monocotyledonous Plants_, 24. _Monocotyls_, 24. _Monœcious_, or _Monoicous_ (flower), having stamens or pistils only, 85. _Monogynous_ (flower), having only one pistil, or one style, 105. _Monopetalous_ (flower), with the corolla of one piece, 89. _Monophyllous_, one-leaved, or of one piece. _Monos_, Greek for solitary or only one; thus _Monadelphous_, stamens united by their filaments into one set, 99; _Monandrous_ (flower), having only one stamen, 100. _Monosepalous_, a calyx of one piece; i. e. with the sepals united into one body. _Monospermous_, one-seeded. _Monstrosity_, an unnatural deviation from the usual structure or form. _Morphology_, _Morphological Botany_, 9; the department of botany which treats of the forms which an organ may assume. _Moschate_, Musk-like in odor. _Movements_, 149. _Mucronate_, tipped with an abrupt short point (_Mucro_), 54. _Mucronulate_, tipped with a minute abrupt point; a diminutive of the last. _Multi-_, in composition, many; as _Multangular_, many-angled; _Multicipital_, many-headed, &c.; _Multifarious_, in many rows or ranks; _Multifid_, many-cleft; _Multilocular_, many-celled; _Multiserial_, in many rows. _Multiple Fruits_, 118, 124. _Muricate_, beset with short and hard or prickly points. _Muriform_, wall-like; resembling courses of bricks in a wall. _Muticous_, pointless, blunt, unarmed. _Mycelium_, the spawn of Fungi; i. e. the filaments from which Mushrooms, &c., originate, 172.