I agree with JD. This is what is termed vegetative reproduction, as opposed to sexual reproduction which this plant will also use, but not likely here.
In its habitat in South America, this plant grows emersed in bog or marsh like conditions, so the roots are fairly wet but the leaves are in the air. It may remain this way permanently, or if close to watercourses it will likely spend half the year submersed when the rivers flood the surrounding forest for thousands of square miles/kilometres and up to 30 feet/9 metres in some areas. All Echinodorus species are like this. And this species is actually Echinodorus grisebachii--I'll return to this momentarily. Fortunately for aquarists, these plants grow very well permanently submersed in the aquarium. However, this causes some changes in reproduction.
As it grows in the wild, the plant would send out the same inflorescence as you're seeing, but it would flower. The flowers are small and white. Like all flowering plants, the flowers pollinate and produce seeds, and that is how the plant reproduces. When grown permanently submersed, the inflorescence will almost never flower, even if it reaches the surface--though this can happen, I've seen it, but rarely. Instead of flowers being produced from the nodes, it produces adventitious plants, or daughter plants. This is vegetative reproduction, which never (so far as I know) occurs in the wild with Echionodorus species unless they are permanently submersed. And very few rivers have submersed aquatic plants, but there are a few.
As JD said, you can plant the roots in the substrate, and the plant will grow larger. You can also leave it, if you like this effect; I presently have four large plants of this species in my 115g tank, each with one, two or three of these inflorescences, containing several adventitious plants. I can create a rather nice effect. I'm attaching a photo from June 2010 which shows dozens of adventitious plants across the top third of this tank, that will give you an idea.
If you do plant the new plant, there will be two plants from the node, and when you remove them (it is best to remove the adventitious plants if you decide to plant them) they will separate easily. Or you can leave them together. In time if you leave them together, they can get huge.
Quickly on the name...this used to be considered a distinct species, Echinodorus bleherae. The Czech botanist Dr. Karel Rataj described and named it in 1970, as Echinodorus bleheri, but the species epithet was changed the following year to bleherae, the feminine rather than masculine gender, because Rataj intended the plant to honour Amanda Bleher, who was the mother of the great explorer Heiko Bleher. His name is given to several plant and fish species, but it was his mother who did much collecting of plants in the Amazon that Rataj wanted to honour here.
But over the subsequent years other botanists have disagreed with Rataj that there were so many species in this genus (Rataj had 62 in his 2004 revision), and finally in 2007 the Finnish botanist Dr. Samuli Lehtonnen carried out extensive phylogenetic analyses of the genus and there are now 30 distinct species recognized. Interestingly, many of these distinct species have sometimes very different forms, and E. grisebachii is one such species. The plants that were previously thought by Rataj to be the species E. amazonicus, E. bleherae, E. parviflorus, and E. grisebachii are in fact the one distinct species. The name must be the first assigned to a species, and here it was E. grisebachii assigned by the botanist John Small in 1909. The other names were all later, so they are now considered synonyms.
Hope that hasn't confused too much, but some find these things interesting.
Byron.
