It was blamed by Padraig Harrington for his failure to finish higher than fourth place in the Malaysian Open in Kuala Lumpur last weekend. Yet according to the US Golf Association, who are widely acknowledged as experts in such matters, it doesn't exist.

So, what are we talking about? Harrington, who had a very costly two-and-a-half-foot miss on the 72nd green, described it as grain; others call it nap. And regardless of what the USGA may claim, it causes nightmares for the most accomplished of putters.

The term grain describes the effect caused by blades of grass all leaning in the same direction. This is generally as a result of the grass growing towards the setting sun and the direction of the natural drainage on a particular green.

To cope with it on his infrequent Ryder Cup visits to the US, Harry Bradshaw talked about the way he would look closely at the cup, to see where the grass was growing over the edge. That would tell him the direction of the grain.

Nobody, not even the USGA, would have argued with The Brad regarding the playing conditions in the 1940s and 1950s. But with the advent of sophisticated agronomy and space-age machinery, experts claim that the influence of grain has been reduced significantly. In fact greens have become so much quicker that grain, where it does exist, is largely irrelevant.

"As far as the (US) PGA Tour events are concerned, grain is not a factor," said Jim Snow, national director of the USGA's Green Section, despite repeated comments to the contrary from TV pundits during the recent Sony (Hawaiian) Open. On the other hand, veteran tournament professional Harry Taylor said: "If you can't read grain on tour, you can't putt."

How then does it affect the roll of the ball? Putts against the grain will be appreciably slower than a player may think, while downgrain putts can be treacherously fast. But the biggest problem occurs when putting across the grain, which will have the effect of pushing the ball off line.

Grain is more prevalent in Bermuda grass which is used in greens in hotter climates, such as those Harrington had to cope with in Malaysia. And it may be a shade more than coincidental that the first two finishers there happened to be Americans, who would have grown up with such conditions.

Bent grass is used in most other areas, certainly in these islands. The greens at Augusta National were Bermuda and relatively slow when Jack Nicklaus set the aggregate record of 271 there in 1966, which was equalled by Raymond Floyd in 1976.

It is revealing to note that despite an overall improvement in playing standards, the record remained unbeaten until 1997 when Tiger Woods shot a stunning, 18-under-par aggregate of 270. Even Nicklaus would readily agree that this was due simply to the fact that, in a major gamble with the weather, Augusta's greens were changed from Bermuda to bent in 1980. The gamble worked and the increase in pace was dramatic.

So, when the USGA claim that grain doesn't exist in tournament greens, what they really mean is that it shouldn't be there, if the surface is properly maintained. But as Harrington would testify last weekend, it's not an ideal golfing world.