Placement of Gymnosperms between Dicotyledons and Monocotyledons is one of the drawbacks: in the system of classification of

• Bentham and Hooker proposed the system of seed plant classification, which is the most well-developed natural categorization system and was published in three volumes in the work Genera Plantarum (1862-83).
• They identified 97,205 seed plant species from 7,569 genera in 202 families, ranging from Ranunculaceae to Gramineae.
• They focused a lot on the perianth's character, particularly the number of whorls (one or two) and if there are two, whether the members of the inner whorl (petals) are free or fused.
• All seed plants were grouped into three categories:
  • Dicotyledons (165 families), Gymnosperms (3 families), and Monocotyledons (34 families).
• Their system of classification was applauded but there were some miscalculations.
  • The system was not phylogenetic.
  • Gymnospermae should not be placed between Dicotyledons and Monocotyledons because Gymnosperms and Angiosperms belong to different classes.
  • Gymnosperms are seed-bearing plants whose seeds are not encapsulated in the ovary and are instead carried on the surface of scales, leaves, or modified as cones.
  • The seed-bearing plants were placed into the primary group Phanerogams by Bentham and Hooker while classifying the plants.
  • Plants with two cotyledons (Dicotyledonae), Gymnospermae (seeds not contained), and Monocotyledonae were placed beneath this (seeds with one cotyledon).
  • This placement of gymnosperms was highly criticised. 

As Bentham and Hooker placed Gymnosperms between Dicotyledons and Monocotyledons, the correct answer to this question is - Bentham and Hooker.