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n. pl. ra·chil·lae (-kĭl′ē)
The axis of a spikelet of a grass or sedge.

[New Latin, diminutive of rachis.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(rəˈkɪlə) or


(Botany) (in grasses) the short stem of a spikelet that bears the florets
[C19: from New Latin, diminutive of rachis]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
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After natural opening of the spathe three rachillae, each bearing 30-40 flowers were collected from middle of the inflorescence just before pollination in the two types of plants.
In some spikes of spikelets, the unisexual flowers may form bisexual spikelets (male and female flowers on a same rachilla) or unisexual spikelets (male and female flowers on different rachillae) (Meert & Goetghebeur, 1979; Timonen, 1998).
Inflorescence erect; prophyll 55 cm long, densely brown setose; peduncular bract to 95 cm long, proximal part covered with brown, 2-4 mm long bristles, these usually not persistent, and grey floccose, flattened, black spines, distal part with flattened, black, up to 5 cm long spines; peduncle to 130 cm long, 3,2 x 4,1 cm in cross section, proximal part tomentose, distal part spiny; rachis 23-38 cm long; rachillae many, to 14 cm long, proximal part 1-5 cm long, glabrous, distal part bearing the pistillate flowers, 3,5-9 cm long, covered with minute, clavate, hyaline hairs, only one pistillate flower inserted 0,2-1,5 cm from the rachis.
Cymophyllus (1 sp.) is distinguished by its unique leaf morphology, short rachillae and white, solitary androgynous spikes.
Inflorescence branching to one order, interfoliar, erect, arching or pendulous, protogynous; peduncle usually elongated, circular to oval in cross section, densely covered in indument, often heavily armed with spines; prophyll short, bicarinate, fibrous, unarmed or armed with small spines or bristles, hidden in the leaf bases; peduncular bract much exceeding the prophyll, spindle-shaped, often rostrate, splitting longitudinally along the abaxial face, persistent or eroding, usually densely tomentose, heavily armed with spines or unarmed; rachis shorter than the peduncle bearing spirally arranged rachillae, each sustented by a narrow triangular bract; rachillae ca.
but differs by having: long-awned pistillate scales; lanceolate, short-awned staminate scales; larger perigynia, achenes, and rachillae; staminal filaments narrower than the anthers; and leaves (abaxial side) papillate-scabrescent (Wheeler, 1997).
Species of section Siderostictae have leaves much broader than in most carices, androgynous spikes often binate or ternate at the inflorescence nodes, beakless perigynia with obtuse pistillate scales, and they occasionally have rachillae with terminal male flowers protruding from the perigynia.
Hexopetion and Astrocaryum are superficially similar in sharing the white indument on abaxial surface of pinnae, flattened spines, robust inflorescence branched to one order with catkin-like staminate rachillae or distal portion of them, pistillate flower(s) basal and considerably larger than staminate ones, fruits large, oval-obovoid, rostrate, spiny, endocarp with superficial black fibers forming a star-like pattern around germinating pores.
Palms referred to as Orbignya are characterized by stamens with coiled anthers, and staminate flowers often densely packed on rachillae (Fig.