Question

The receptacle is flattened at the top and bears numerous sessile flowers in centripetal order:
(A) Cyathium
(B) Catkin
(C) Umbel
(D) Capitulum
(E) Verticillaster

Answer 1

Inflorescence tells about the arrangement of flowers in a plant. The pattern of inflorescence differs between flowers. Some bear cylindrical-type flowers, some are cup-like, flattened, etc.

Complete answer: Inflorescence is defined as a cluster of flowers on a branch of a plant.
A. Catkin inflorescence is a compact unisexual having cylindrical flower clusters with no petals. It matures and falls down as a single unit like mulberry, poplar, willow, etc.
B. In the Umbel, all the pedicellate flowers arise from a single point in a centripetal fashion because the peduncle is reduced.
C. Cyathium is an inflorescence that consists of a small cup-like structure enclosing a female flower and several male flowers, It is the characteristic features of plants in the genus Euphorbia.
D. Verticillaster inflorescence is an inflorescence in which the flowers are arranged in a seeming whorl, that consists of a pair of opposite axillary, usually sessile cymes, as in many mint plants. It is common among Lamiaceae.
E. Capitulum (Racemose head: in Capitulum, the peduncle is somewhat flattened to form a receptacle that bears small sessile flowers called ‘florets.’ The latter are of two types, tubular and ligulate. The florets are arranged in a centripetal fashion, that is, younger inflorescence towards the center and the older towards the periphery. The inflorescence is surrounded by one or more whorls of bracts called ‘involucre’. Capitulum inflorescence is found in family Compositae. Some of the examples are Tagetes, Zinnia, Sunflower, etc. It may be tubular homogamous (Ageratum), ligulate homogamous (Sonchus) or heterogamous (sunflower).
Hence, the correct answer is option D.

Note: In Sunflower, the central disc florets are bisexual and tubular, while the peripheral ray florets are sterile and ligulate. Many members have composite flowers in the form of flower heads (capitulo) surrounded by involucral bracts.