Q. Basis of Classification on Form-relationship principle?
As pointed out earlier, this system is mainly based on Form-relationship principle. thus the various genera were. grouped under orders and different orders under Cohorts were based on the overall similarities and differences. A few orders which could not be satisfactorily accommodated in any Cohort, were treated as an anomalous orders (Ordines Anomali) such as Moringa, common name Sajna, Drumstic tree under Moringeae.
The outline and basis of classification are given below:
1) Phanerogams (Flowering plants or seed plants) were classified into 3 classes namely, i) Dicotyledons, ii) Gymnosperms and iii) Monocotyledons
This division is based on reticulate venation versus parallel venation, 4-5 merous -flowers versus 3-merous flowers, 2-cotylodons versus 1-cotyledon in seed in Dicotyledons and Monocotyledons respectively. They have placed Gymnosperm , in between the Dicots and Monocots as' the group Gymnosperms possess naked, seeds..
2) Dicots are further splitted into 3 subclasses:
a) polypetalae
b) Gamopetalae, and
c) Monochlamydeae
This division is based mainly on the presence or absence of petals, and their fusion. For example, in Polypetalae the petals are present but free whereas in Gamopetalae the petals are fused. On the other hand in Monochlamydeae, no distinct petals are present but perianth is present which may be 1 or 2-seriate.
3) Polypetalae is further classified into 3-series
a) Thalamiflorae,
b) Disciflorae, and
c) Calyciflorae
This splitting is mainly based on the position of ovary in relation to thalamus.
4) Thalamiflorac has 6 Cohort (present day's Orders and 34 orders (present day's families). The starting order is Ranales and Ranunculaceae as the starting or the first family. The last or the sixth order is Malvales with Tiliaceae as the last family of this series.
5) Disciflorae which possesses a well developed disc with superior ovary has 4 orders and an anamolous order namely Ordines Anomali. The total number of families in this series are 23. The starting order is Geraniale s with Linaceae as the starting family where as Ordines Anomali is the ending order and Moringaceae as the last family.
6) In Calyciflorae perigynous or epigynous flowers are found which have 5 orders and 27 families. The starting order being Rosales with Connaraceae as the starting family where as the last or the ending order is Umbellales and Cornaceae as the ending family.
7) The sub class Gamopetalae where the petals are fused is divided into 3 series, namely: i) Inferae, ii) Heteronierae, and iii) Bicarpellatae
This splitting is mainly based on the number and position of carpels. For instance in the series, Inferae, as the name indicates, bicarpellary, syncarpus, inferior ovary is present, while in the case of Heteromcrac, the carpels' are always more than two. On the other hand in Bicaipellatae, it is always bicarpellary,
syncarpous with superior ovary. The total number of order in Gamopetalae is 10, 3 in Inferae, 3 in Heteromerae and 4 in Bicarpellatae. Whereas the families are 45 in all, 9 in Inferae, 12 in Heteromerae and 24 in Bicarpellatae
8) Inferae has 3 orders namely Rubiales, Astcralcs and Campanulales. The starting family is Caprifoliaceae while the ending or terminating family is Campanulaceae
9) Heteromerae also has 3 orders viz. Ericales,. Primulates and Ebenales. The starting family is Vacciniaceae where as the last family is Styraceae.
10) Bicarpellatae has 4 order namely Genfianales, Polemoniales, Personales and Lamiales. Further, the first 2 orders i.e. Gentianales and Polemoniales have actinomorphic flowers while ,Personales and Lamiales ar'e characterised by zygomorphic flowers. The starting family is Oleaceac while the last or ending family is Labiatae or Lamiaccae. The family Plantaginaceae has been accommodated under Osdines Anomali.
11) The subclass Monochlamydeae is divided into 7 series and one series as Ordines Anomali. The starting series being curvembryeae with Nyctaginaceae as the starting family where as the ending series being Ordines Anomali with Ceratophyllaceae, a hydrophytic family, as the ending family.
12) The Class Gymnospcrmae is placed in between the Dicots and Monocots with 3 families namely Cycadaceae, Coniferae and Gnetaceae.
13) The Class Monocotyledons is divided into 7 series. The starting one being Microspermae with Hydrocharitaceae as the starting family. The family Orchidaceae is also included in the series, whereas the lust series being, Glumaceae with Gramineae (Poaceae) as the last family.