Question

A scorpioid cyme having all the flowers in the same plane is ____
(a) Rhipidium
(b) Cincinnus
(c) Dreponium
(d) Bostryx

Answer 1

Hint: The scorpioid cyme, a type of cymose inflorescence that has all the flowers arranged on the same plane is the Rhipidium. Example: Solanum nigrum. The arrangement of the flowers is in a zigzag pattern.

Complete answer: Inflorescence, in flowering plants, can be described as a group or cluster of flowers arranged on a stem or system of branches, whereas a cyme is a flat-topped cluster of flowers in which the central or terminal flower opens first followed by the peripheral flowers. There are six major types of inflorescence:
1. Racemose Inflorescence
2. Cymose Inflorescence
3. Compound
4. Cyathium
5. Verticillaster
6. Hypanthodium.
Cymose Inflorescence may show Helicoid, (b) Scorpioid, and (c) Sympodial cyme.
In scorpioid cyme the lateral branches develop on alternate sides, forming a zigzag, seen in Gossypium (cotton), Drosera (sundew), Heliotropium, Freesia.

Rhipidium is a scorpioid cyme where the arrangement of flowers on a plant is alternate and somewhat fan like.

Note: Another type of cymose inflorescence is helicoid cyme or one-sided cyme where the main peduncle ends in flower. It gives lateral branches on one side which also ends in a flower. This branch gives another branch on the same side to form a helix. eg. : Myosotis