Takhtajan Classification

Arman Takhtajan was born in 1910. He was head of department of higher plant at Komarov botanical institute in Russia. Takhtajan Classification was first published in 1942. In 1959 eloborated a system of classification appeared in German in his die evolution Der angiosperm. A new version of Takhtajan's classification appeared in botanical review. This system is basically inspired by bessey hallier tradition considering evidence from filled like morphology anatomy, embryology, cytology, palanology etc.

Also read- Engler and prantl classifiaction

Main Criteria

Growth Habit - Simple Woody  plant  ~ Large tree ~ herb 
Leaves~ Simple ~ Pinnate ~ Palmate ~ Compound ~ alternate ~ opposite 
Node-  Pentalocular to unilocular 
Wood anatomy - Vessels with scaly form performation plate. 
Inflorescence - Cymose~ Racemose ~Solitary
Floral Part - Andoecium leaf like microsporophylls with microsporangia with margin. 
Pollen Grain -  unsculptured exine is primitive than sculptured pollen. 
Gynoecium- Epicarpal to Syncarpal 
Ovule - Bitegment ~Unitegment
Seed - Medium size of seed, Smear and large minute embryo or abundant angiosperms.

Also read - Hutchinson classification

In 1977 Takhtajan revised his classification and now two class include 11 sub-classes 6 in magnoliopsida and 5 in liliopsida. In 1980 Takhtajan divided Magnoliophyta (Angiosperm) into two class Magnoliopsida and Liliopsida.

In all the recognised 92 order and 410 family.

Source Wikipedia

Takhtajan classification is based on 67 phyletic principle. Some of the important criteria used by him to evaluate the relative degree of advancement of flowering plants are as follow:

Also read - Bentham and Hooker classifiaction

1. Woody plants are primitive than herbaceous plants.
2. Xylem fiber evolved from trachieds to libriform fibers, through fiber trachieds.
3. Pentalcunar or trilacunar nodes are primitive to unilacunar nodes.
4. Alternate leaf arrangement is primitive while parellel venation is most advanced. 
5. Cymose inflorescence is primitive than Racemose.
6. Flower with an indefinite or variable number of floral parts are primitive.
7. Pollen with unsculptured exine is primitive than sculptured pollen.
8. Apocarpous gynoecium is primitive.
9. Bitegmic ovules is primitive than unitegmic ovules, while anatrooous ovule is most primitive
10. 8 nucleated polygonum type female gametoohyte is most primitive.
11. Mesogamic and Chalazogamic condition have evolved from porogamic condition.
12. Among fruits many seeded follicle is most primitive.

Merit and De-Merit Of Takhtajan classification

Merit - 

1. The Dicot (Magnoliopsida) has been discussed prior to Monocot (Liliopsida).
2. The family are small homogenous units mode up of closely related genera.

De-Merit -

1. The main objection to Takhtajan's classification is his derivation of monocotyledons from the stocks ancestral to the Nympharales.
2. The extremely norrously defined Taxa in this system has resulted in the unwarranted splitting of related groups.