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A Handbook of Biology

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Asymmetric (irregular): Here, a flower cannot be divided into two similar

halves by any vertical plane passing through the centre. E.g. canna

BÅSËD ØÑ ÑÜMBËR ØF FLØRÅL ÅPPËÑDÅGËS, FLØWËRS ÅRË ÇLÅSSÏFÏËD ÅS

FØLLØWS:

Trimerous: Floral appendages are in multiple of 3

Tetramerous: Floral appendages are in multiple of 4

Pentamerous: Floral appendages are in multiple of 5

BÅSËD ØÑ THË PØSÏTÏØÑ ØF ÇÅLÝX, ÇØRØLLÅ ÅÑD ÅÑDRØËÇÏÜM ÏÑ RËSPËÇT ØF

THË ØVÅRÝ ØÑ THÅLÅMÜS, THË FLØWËRS ÅRË ØF 3 TÝPËS:

Hypogynous: Here, gynoecium occupies the highest position while other

parts are situated below it. The ovary is superior. E.g. Mustard, China rose

and brinjal. (AIPMT 2015)

Epigynous: Here, the margin of thalamus grows upward enclosing the ovary

completely and getting fused with it. Other parts of flower arise above the

ovary. The ovary is inferior. E.g. Guava, cucumber, ray florets of sunflower.

(NEET 2020)

Perigynous: Here, gynoecium is situated in the centre and other parts are

located on the rim of the thalamus at the same level. Ovary is half inferior.

(NEET 2020) E.g. Plum, rose, peach.

01

02

03

(a

(

)

b)

(c)

(d)

Floral position on thalamus : (a) Hypogynous (b and c) Perigynous (d) Epigynous

2. PÅRTS ØF Å FLØWËR

Å. ÇÅLÝX

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It is the outermost whorl of flower. It is made of

sepals.

Calyx