I don't think the Hist are proven to be the same as the walking city of Falinesti. That's a speculation that I've never heard on these forums until this past week or so.
After looking into Falinesti, there are some interesting connections...
1) Bosmers are the "tree sap people" and Argonians are "people of the root" and lick Hist sap
2) It seems like a huge coincidence if Falinesti was not a Hist, and just coincidentally another type of moving tree
3) Y'ffre (Bosmer deity of the forest) turned into the first Elnofey, the Hist coincidentally were also around at the beginning
4)
The first mortals were turning into plants and animals and back again
supports the idea that Argoinians and Hists are the same organism experiencing a different stage in their life cycle\
Animals licking trees is also something that goes on in the real world. A quick google search came up with lemurs licking trees because the coevolved with the plants and act as pollinators. Animals also spread seeds, which may or may not be what Argonians are doing outside of Black Marsh... Animals can also digest the seed and deposit it in the soil when they go #2. Are argonians doing this when they lick the Hist? Doesn't seem likely but its not impossible.
According to Pete Hines in the Argonian Compendium, argoinians are ovoviviparous. And the young of ovoviviparous amphibians are sometimes born as larvae, and undergo metamorphosis outside the body of the mother. So Argonians may experience some sort of metamorphosis in their life. BlueDev also mentions in the article that whether an Argonian lays eggs or not depends on their climate. In a wikipedia article on vivipary, its says
There is a relationship between six-determining mechanism and whether a species bears live young or lays eggs. Temperature-dependent six determination does not work in the sea, so marine viviparous species use genotypic six determination (six chromosomes)[1].
Temperature-dependent six determination (TSD) is a system in which the temperature of neighboring eggs determines the six of the organism that hatches[1]. It is most prevalent and common among amniote vertebrates that are classified under the reptile class[1], but is also used among some birds, such as the Australian Brush-turkey. It differs from the chromosomal six-determination systems common among vertebrates. It is a type of environmental six determination (ESD); in other ESD systems, some factors such as population determine the six of organisms (see Polyphenism).
In the argonian compendium it says you are more likely to find eggs in well established communities in warmer climates. This could mean that there are more females being born in warmer climates that are also laying eggs... This sort of environmental effect on Argonian phenotypes might also include some sort of hormone released in Hist sap.
PS = apparently http://www.imperial-library.info/mwbooks/corpse_preparation.shtml