Should I place glue on the entire length of a long mortise and tenon?

It’s cross grain so, no. Glue 3-4” in the middle and use pegs through slots in the tenons toward the ends.
I think Arts and Crafts gets square pegs.

I can’t really see exactly what the picture is trying to show.

-- Gary - Never pass up the opportunity to make a mistake look like you planned it that way - Tyler, TX

Do you have a shop drawing?

If there is another rail or is the shelf the only thing tying the leg assemblies.

You are not going to want to glue that whole thing due to wood movement.

Show us a drawing of somekind.

-- -John "Do I have to keep typing a smiley? Just assume it's a joke." www.flickr.com/photos/gizmodyne

No if it is like I’m thinking You should only glue in the middle and use pegs like Gary states. here is a picture of a breadboard end on a table I made.

I only glued the middle one the outer ones float.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware karson_morrison@bigfoot.com †

Hopefully the drawings will shed more light.

Here are two different views from my Sketchup shop drawing. The bottom shelf has tenons on both ends. The shelf is being supported on both ends (only the ends, no side rails) by aprons.

-- Joe Heskett---Illinois

It looks like the shelf has width and will shrink and expand. The end it is going into will keep that movement from happening. The shelf will split.

It has to be able to move. I assume it is solid wood and not plywood. Plywood won’t expand and contract. You would be better off putting a small shelf in just the middle or making a bunch of smaller shelf boards like this in the end panel.

Like this table top.

But have it go into table end.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware karson_morrison@bigfoot.com †

You might think about adding rails at the top. You could do a drawer and would add extra support.

If not, I agree with Karson. Glue in the middle only and a peg is also possible. You could dowel in from the bottom through the middle and then it would be hidden. Just to keep the tenon from pulling out in the future.

Are you going to glue up the side assemblies first?

-- -John "Do I have to keep typing a smiley? Just assume it's a joke." www.flickr.com/photos/gizmodyne

Karson, The shelf is made out of QSWO. I made the mortise 1” wider (1’/2” each side) than the tenon width to allow for movement. Wouldn’t that be enough?

gizmodyne, Great eye!! I built rails (stretchers) for the top i just didn’t load the drawing that included them :-) The table is a gift for my wife and she didn’t want any drawers at the time. My plan is to glue up the side assemblies first and then glue the bottom shelf and rails (stretchers) to the side assemblies.

Thank you both for your help. I have come to find LumberJocks a great community of people willing to share thoughts and ideas and talent.

-- Joe Heskett---Illinois

I think you have left plenty of room.

-- -John "Do I have to keep typing a smiley? Just assume it's a joke." www.flickr.com/photos/gizmodyne

As the others have said, I think you have plenty of room for movement. Gluing only a portion of the tennon is a good way to go. Generally I think most people glue the middle and let the ends float. In your particular application though, I see a strength problem with the legs, if you just glue it like that. A lower stretcher would solve that….but it would be a big design change too.
As an alternative, you could put a dowel (from below) in the ends of the tennon. You just need to cut a slot in the tennon so that the shelf can slide along the length but not “pull out”.
You could also glue the tennon in the front and allow all of the movment to go front to back. This is especially helpful in stained projects where shrinking may expose un-stained areas.

It is too late this time…...but a sliding dovetail can do the same thing w/o having to dowel the other end. You put your glue at the front, socket only, so it doesn’t get spread over the hole joint. Then, if you need to (because it would be exposed) you can cut a piece to fill in the back of the slot.