Xylem cells are elongated cells with lignified secondary thickening of the cell walls. Xylem cells are specialised for conduction of water, and first appeared in plants during their transition to land in the Silurian period more than 425 million years ago (see Cooksonia). The possession of xylem defines the vascular plants or Tracheophytes.
hobo. a hobo is an itinerant worker, a career which sprang up during the depression. A hobo, unlike a bum or a tramp, is more than willing to work, but mostly for a short duration, as their main impetus is travel, the love of the journey above the actual destination.
hobo Be careful when you call a vagrant or homeless person a hobo â although this is exactly what the word means, it is a somewhat offensive term. The end of the nineteenth century brought the start of the word hobo in the Western United States. No one is certain where the word came from, although there are a couple of educated guesses. One possible origin is the English word hawbuck, which means country bumpkin, while another is the common working man's greeting or call during the building of the railroads in the West, ho, boy!