We've had several postings on the topic of "what is a bulb" lately, and this most recent one by David Ryle prompts me to jump into the fray. I'm by no means rigid about this: fitting an a-priory concept such as "bulb" to the happenings in the real world always seems to involve a bit of fudging. David Ryle wrote: "All plants that grow from what would commonly be thought of as a bulb etc; are known botanically as geophytes. By definition a geophyte is a plant that grows from a modified leaf that has evolved into a storage organ." David gives us a definition; definitions by their nature are neither right nor wrong, they're just definitions. To the extent that they work, we use them. But the one he gives does not work for me. To say that "a geophyte is a plant that grows from a modified leaf that has evolved into a storage organ" is to approximate the traditional, conservative definition of "bulb", but it does so to the exclusion of many other geophytes such as those which grow from corms or other stem tissues. It is the bulb (in the narrow sense) which has as a primary storage tissue modified leaves. The scales of a lily, for instance, are modified leaves. The major food storage parts of a tulip bulb are modified leaves. Crocuses are geophytes, but they do not have modified leaves as their major storage tissue; their major storage tissue is stem tissue. Since the one thing all geophytes that I know have is stem tissue in one form or another, I think it makes sense to set up a definition where the role of stem tissue is central. A bulb, in a sense, is a corm supplemented with storage tissue in the form of modified leaves. I think of bulbs such as lily bulbs or tulip bulbs as a corm (the so-called basal plate, which I prefer to call the perennial stem) surrounded by modified leaves which serve as storage tissue. Since the plants which form bulbs, corms and so on are not always related (the majority are monocots, but some are dicots only very remotely related to the monocot bulbs), it should not surprise us that the observed structures do not fall into neat categories. For instance, what should we call the structure from which Achimenes grow? I think of it as an elongated basal plate surrounded by modified storage leaves, superficially similar to the underground parts of some native North American lilies. I'm pretty much alone in calling the Achimenes structure a bulb, but even those who insist that that structure cannot be a bulb will call the similar structure in the lilies a bulb. One might say that if the primary storage tissue is leaf-derived, then it is a bulb. If the primary storage tissue is stem derived, then it is something else. I've never had the patience to remove all the little modified leaves from an Achimenes bulb to weigh them and then compare that weight to that of the structure to which they were attached. But you get the idea. Since Achimenes are gesneriads, we should not be surprised that it is difficult to fit them into a scheme originally devised to describe the storage structures of liliaceous plants. When I look at plants like Echeveria, Sempervivum and such I can't help seeing the gross similarity to bulbs like lily bulbs. There is, in fact, a purportedly epiphytic lily species named Lilium sempervivoides. Another intermediate condition is seen in Florence fennel, a cultivated form of fennel in which the base of the petiole is swollen to form, with the petioles of other leaves, a bulb-like structure. This "bulb" grows partially buried, partially exposed. Is it a geophyte? Does a bulb have to be a geophyte? Can an epiphyte such as the lily mentioned above be a geophyte? It seems to me that we can't be too strict about any of this: there are too many intermediate forms to allow definitions which are both tight and workable. Also, in the discussion above the emphasis is on structure. But surely life cycle should enter into any definition of geophyte. The structure of a Sempervivum might suggest a bulb to some, but the life cycle of a Sempervivum certainly doesn't. Florence fennel does not have an underground dormant phase - bulb or not, it's hardly a conventional geophyte. I think we need to keep some wiggle room in our concepts. Jim McKenney jimmckenney@jimmckenney.com Montgomery County, Maryland, USA, USDA zone 7, where I've been hand pollinating - apparently successfully - the big pink Eremurus to get seed. My Virtual Maryland Garden http://www.jimmckenney.com/ Webmaster Potomac Valley Chapter, NARGS Editor PVC Bulletin http://www.pvcnargs.org/ Webmaster Potomac Lily Society http://www.potomaclilysociety.org/