Back to (older) post by bunkfree: they say isotype not isotope. Here is what I found on net (Wiki): To be an isotype of a particular gene family means to belong to a set of genes that encode functionally similar proteins. Usually, isotypes that belong to a particular gene family are duplicate copies of the same gene that arose because of a mistake during DNA replication. As the species continues to evolve, those duplicated genes are passed on from generation to generation until every member of the species has a copy. Each of those genes have since undergone mutations of their own, such that they diverge slightly in structure and function, giving rise to the different isotypes known today.

Photo #2 is a Kalanchoe daigremontiana - it propagates prolifically from tiny plantlets growing alongside the leaf edges (you could see couple of babies on one of the leaves). In some areas, they could become weedy :)

It is gorgeous plant. Looks quite old. I wouldn't think it is Portulacaria afra...I think Gill is right. Even if trunks of PA get woody as they age, wouldn't at least tips of very new branches be more reddish? My plant is much smaller and not very old, here is a trunk of it (more segmented, and segments look bit 'puffy'):The leaf growth patter seems to be just little different (not as much as rosette as on OP's plant), and leaves are more uniform in size and shape. New growth branches are more soft-juicy and reddish looking:Of course, I am just judging by what I have seen on my small plant and could be wrong...

Here are more photos