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49. Ericaceæ. 50. Pyrolaceæ. 51. Monotropaceæ. 52. Aquifoliaceæ. 53. Oleaceæ. 54. Apocynaceæ. 55. Gentianaceæ. 56. Polemoniaceæ. 57. Convolvulaceæ. 58. Boraginaceæ. 59. Solanaceæ. 60. Orobanchaceæ. 61. Scrophulariaceæ. 62. Labiatæ. 63. Verbenaceæ. 64. Lentibulariaceæ. 65. Primulaceæ. 66. Plumbaginaceæ. 67. Plantaginaceæ.

68. Amaranthaceæ. 69. Chenopodiaceæ. 70. Scleranthaceæ. 71. Polygonaceæ. 72. Thymelaceæ. 73. Santalaceæ. 74. Aristolochiaceæ. 75. Empetraceæ. 76. Euphorbiaceæ. 77. Callitrichaceæ. 78. Ceratophyllaceæ. 79. Urticaceæ. 80. Ulmaceæ. 81. Elæagnaceæ. 82. Myricaceæ. 83. Betulaceæ. 84. Salicaceæ. 85. Cupuliferæ. 86. Coniferæ. 87. Dioscoreaceæ. 88. Trilliaceæ.

89. Hydrocharidaceæ. 90. Orchidaceæ. 91. Iridaceæ. 92. Amaryllidaceæ. 93. Liliaceæ. 94. Melanthaceæ. 95. Restiaceæ. 96. Juncaceæ. 97. Butomaceæ. 98. Alismaceæ. 99. Juncaginaceæ. 100. Typhaceæ. 101. Araceæ. 102. Orontiaceæ. 103. Pistiaceæ. 104. Naiadaceæ.

105. Cyperaceæ. 106. Gramineæ.

Plants being arranged under the Natural System according to general characters only, some genera of certain orders will be found to possess the structural form of a different subclass to that in which the order is placed. For instance, though most Leguminosæ have petals and stamens arranged in the manner characteristic of the subclass Calycifloræ, some exotic plants of that order have no floral envelope, and would therefore be referred to Monochlamydeæ by the inexperienced student, while a few British species having hypogynous stamens would seem to be naturally placed in the Thalamifloral division. To avoid the confusion thus arising, a more