Would this be a special gardening-type heating pad, or would a standard home-use type pad work?

Several seed catalogs that I have received have what is called a heating mat, upon which the seed flats are directly placed. One such place is Park Seed Company in Greenwood, S. C., as well as in catalogs from several other places. If you are referring to a heating cable, which we place outside in a structure, similar to a cold frame, but with the addition of the heating cable underneath soil or other soiless mixtures, it is called a hot bed. Horticultural Supply Company, Inc. in Wisconsin, approximately the same address as R. H. Shumway, has several sizes of the heating cables, but I do not know, but I think that the heating mat is what you want. I think the heating mat only comes in one size, but to cover a bigger area, you just order a greater number of heating mats. Heating cables are harder to find than heating mats, because just about any mail-order seed company has the mats, which are for propagating a smaller amount of plants, while the heating cables are only in two catalogs that we received, and are mainly for plant propagation outside.

If you are thinking about standard heating pads like the ones you use when you have a sore back, forget it. They all have automatic turn off now. The least expensive ones for warming flats are preset to heat 10 to 20 degrees above ambient air temps. In most cases that is enough control. If you do need more exact control there are separate controls like a timer you can plug one of those into. They run around $30 each or more. I have heard some get around that by plugging a power strip into the control and then plugging the mats into the strip. Since I don't know what the amperage is on the controls I don't know how good that solution is.
There are several companies that use that same address. Plantation and I think Farmers also get their mail there so I assume they are all just desks in a corner somewhere using the same warehouse and mail facility. I don't get seeds or plants from them so I don't much care, but it does seem strange. Sandy

I have 20 centrosema virginianum seeds I would like to trade for how many ever kennedia coccinea seeds you have to offer. If you are interested email your address and I'll send you mine. I will send my seeds in a padded envelope.

Dave.