Mention the demerits of Sexual system of classification?

Explanation

1. Totally unrelated plants were kept in a single group, whereas closely related plants were placed in widely separated groups. ,
(i) Eg: Zingiberaceae of monocotyledons and Anacardiaceae of dicotyledonous were placed under the class Monandria since these possess single stamens.
(ii) Prunus was classified along with Cactus because of the same number of stamens.
2. No attempts were made to classify plants based on either natural or phylogenetic relationships which exist among plant groups.