Raceme and glumes arranged in two opposite rows along the spikelet. Examples occur on rice (species "Oryza sativa") and wheat (genus "Triticum"), both grasses. An ament or catkin is very similar to a spike or raceme, "but with subtending bracts so conspicuous as to conceal the flowers until pollination, as in the pussy–willow, alder, [and] birch...". These are sometimes called amentaceous plants. A spadix is a form of spike in which the florets are densely crowded along a fleshy axis, and enclosed by one or more large, brightly–colored bracts called spathes. Usually the female flowers grow at the base, and male
Helitron (biology) Helitron (biology) Helitrons are one of the three groups of eukaryotic class 2 transposable elements (TEs) so far described. They are the eukaryotic rolling-circle transposable elements which are hypothesized to transpose by a rolling circle replication mechanism via a single-stranded DNA intermediate. They were first discovered in plants ("Arabidopsis thaliana" and "Oryza sativa") and in the nematode "Caenorhabditis elegans", and now they have been identified in a diverse range of species, from protists to mammals. Helitrons make up a substantial fraction of many genomes where non-autonomous elements frequently outnumber the putative autonomous partner. Helitrons seem to have a major role