Looks like you're just missing the base cap. I wouldn't replace the entire baseboard, small and new would not work. Kuiken Bros. and many others have a great on-line selection of mouldings and there are several types of base caps. Take a look and see what you like. Stain to match and you're all set.

I was lucky enough to find a section of base for my kitchen in the garage--just had to strip the mint green paint from it--the base cap I had to find at a local antique mall--saved money over having new milled, and I was lucky that I only needed about 5-7 feet of it.

Salvage shops, and some larger antique shops will sell trim removed from houses, as might a local ReStore.