I was taught, perhaps wrongly, that tubers are composed of stem-like, not root-like tissue. The example used in high school was not Dahlia or Begonia, where the stem is attached to the tuber, but white potato, where the tuber is clearly separate from the stem. Orchids, gosh, I'm not sure -- one could certainly make a case for considering (some of) them succulents or geophytes. ----- Original Message ---- From: "bonaventure@optonline.net" <bonaventure@optonline.net> To: pbs@lists.ibiblio.org Sent: Thursday, August 21, 2008 11:10:34 AM Subject: Re: [pbs] What is a succulent What about the "tubers" of Bletilla? Some genera of terrestrial orchids (eg. Cyrtopodium, Eulophia) have species with those underground structures, yet other species with them partially buried and others with them totally exposed where they are termed "pseudobulbs" yet they are completely made up of stem tissue?? Isn't "tuber" a swollen root structure, as in Dahlia and some species of Impatiens, as opposed to "corm" made up of stem tissue? Bonaventure _______________________________________________ pbs mailing list pbs@lists.ibiblio.org http://www.pacificbulbsociety.org/list.php http://pacificbulbsociety.org/pbswiki/