Palms in the plant kingdom.
A gentle introduction to palm biology.
I didn’t want to put this page in as I thought it too technical, but a close friend insisted that someone might be interested to know more about these fascinating plants - so here goes. Incidentally I'm not the greatest expert either, as I have come late to their study - so any mistakes I make, well -  I will not think badly of anyone who wants to correct or add to the following. Web-sites which  provide much of the following  information  in much greater detail are listed at the end of this section.

Major group
Palms are in the same major plant group as grasses, bamboos etc. This is a major group called the monocotyledons. Their features are the long strap like leaves, and the veins in the leaves that run parallel to each other:

Monocots and Dicots
Anyone who has grown sweet corn will also know that the first leaf that emerges from the ground is a single leaf, this the same with all monocotyledons and is where the name arises (mono - one,cotyledon - seed leaf). All other flowering plants have two seed leaves, and regularly they appear above ground as the plant germinates. These are called dicotyledons. The other main feature of  monocots is their internal structure: the veins in their trunk are commonly distributed unevenly across the trunk. This is unlike dicots which have a regular arrangement of their veins in a circle:--
Age

As far as I can gather so far, fossils suggest that palms have been around since the Mesozoic Era, and within that the *Cretaceous Period -- at least 70 million years ago. At least one expert suggests that palms may not just be monocotyledons, but that they may be the forebears of all modern monocotyledons! However, this does not seem to be the currently accepted view.
Forms of germination

Dicot stem

Monocot stem

Internal veins

normally - i.e. the root and shoot appear next to the seed. Subsequent reading on this tells me that these two types of germination are called remote (where the shoot comes out of the root) and adjacent. Although many features are used in the grouping of palms, this feature varies from one set of oids to another in an interestingly consistent way as follows:
I now discover that the first seedling root is called the”cotyledonary
petiole.” It is not the root at all. The first  seedling shoot (plumule)
develops from the swelling I describe. I’m also informed that the actual cotyledon or seed leaf remains inside the seed as an organ called the “haustorium”. The haustorium is absorptive and transfers nutrients to the young seedling from the food store (endosperm) in the seed. In adjacent germination,  the first structure to appear  is called the “button” . This is a round shiny structure, flattened on the top.  (See photos alongside).The root and shoot grow out  from the bottom and top of the button.  A haustorium remains inside the seed absorbing food from the endosperm, just as with remote germination.

More grouping
A more recent grouping, (or taxonomy as it is called ) of the palms is to be found on PACSOF (see below for web-site). This is a much more detailed an academic source than mine.  And , as it  seems to be based on a reference work that used  such esoteric considerations as chloroplast  DNA,  it is far more likely to reflect the true relationships of  palms to each other. However, it does not give any reference to the root formation of the groups.  Also it does not quite accord with the classification given in E. Britannica. So I will be ‘ornery’ and stick to my  ‘oids ‘ grouping above for the moment.
But seriously, if you are looking for a  more up-to-date taxonomy, then I

There are about 2,800 species of palms, put into 200 genera. These genera are then lumped into several major groups or ‘..oids’, which share similar features. An interesting feature of the palms -- well it was to me when I first observed it as my palm seeds germinated -- is how the shoot appears. In many of the easier palms -- the Date palm Phoenix for example, the shoot comes out of the root part way along its length. Also see “animation”.
This struck me as being so strange I’ve photographed it in a date palm; see below.
More strangely, other palms, Neodypsis for example, do germinate

Button

Root

Button

suggest you consult the above site. The site also has far more
details of the evolution and fossil record than mine.  

*For those wanting a quick reference to a web site offering  info.on geological time scales etc. then Douglas Hendersons Illustrations of Earth History (http://gallery.in-tch.com/~earthhistory/) is an interesting one to
visit.   
                              
Very detailed information about palms, including  distribution, economic importance, ecology, evolution, taxonomy: Palm and Cycad Societies of  Florida (PACSOF)