Investigators believe seeds and other natural material found on the shoes of Katherine Phillips' father could be crucial to the location of the body. The 4 1/2-month-old girl disappeared two years ago this weekend from the Ludington area.
The case is being treated as a homicide. Sean Phillips is in prison after being convicted last year of secret confinement of his daughter, the only charge filed so far. Authorities accused him of taking her from her mother.
More than 100 people showed up at a school auditorium in Ludington — 80 of them with botany expertise.
"I volunteered because I want to have closure for the families in the area," Jeff Mount, an area school superintendent with a biology degree.
The search will last two days and include experts from Michigan State University, the University of Michigan and the Chicago Field Museum.
"I have been interested in the case since day one and botany is one of my favorite hobbies. Put the two together and here I am," local writer Joan Young said.
Authorities told searchers to watch for certain types of moss and sedge. MLive.com reported Friday that volunteers were told to put plants in plastic bags for later inspection. Depending on the results, police could return to a specific site and dig.
"It's going slowly," said Bob Brown of the Mason County sheriff's office.
Owosso resident Robert Kavetsky, who recently retired from the U.S. Fish and Wildlife Service, volunteered. He said he was inspired partly by history: A family member was buried in a mass grave during the Russian revolution in 1917.
"They've given us good keys and pictures," Kavetsky said. "They sent us information before to think about. It's a fairly narrow list they're looking at."