An online encyclopedia's article on cellulose says that cotton is roughly 90% cellulose, and that wood is about 50%. Just curious as to the cellulose content of some of the plants we eat like celery and apples? Anyone know?

All I've been able to come up with is this 70 year old article in the Journal of Nutrition <removed>, which lists most plant foods as composed of 0.5 to 6.5% cellulose. It also lists up to 5% of each food item as being "undetermined" so I don't know how reliable these figures are.