Last week the question was: What happened to this sweet potato vine?
The abnormal wide growth of this stem is called fasciation. The cause of fasciation is not totally understood, though it is thought to be a hormonal imbalance from a genetic mutation. Fasciation is fairly common in sweet potatoes and does not affect the yield. For more info, take a look at this page from Perdue.
Here is this week’s question: Which grassy weed is this that produces stolons that are shaped like torpedoes at their tips?