Find this block in void doubleclick():

} else
if (((items[x].id1==0x0C)&& 
((items[x].id2==0x4f)||(items[x].id2==0x50)||(items[x].id2==0x51)||
(items[x].id2==0x52)||(items[x].id2==0x53)||(items[x].id2==0x54)))) //cotton plants
{
if (!chars[s].onhorse) action(s,0x0D);
else action(s,0x1d);
soundeffect(s,0x01,0x3E);

inititem(itemcount);
items[itemcount].ser1=itemcount2/16777216;
items[itemcount].ser2=itemcount2/65536;
items[itemcount].ser3=itemcount2/256;
items[itemcount].ser4=itemcount2;
items[itemcount].id1=0x0D;
items[itemcount].id2=0xF9;
items[itemcount].cont1=items[packitem(currchar[s])].ser1;
items[itemcount].cont2=items[packitem(currchar[s])].ser2;
items[itemcount].cont3=items[packitem(currchar[s])].ser3;
items[itemcount].cont4=items[packitem(currchar[s])].ser4;
items[itemcount].layer=0;
items[itemcount].x=20+(rand()%100);
items[itemcount].y=40+(rand()%80);
items[itemcount].z=9;
items[itemcount].pileable=1;
items[itemcount].type=0;
int k;
for (k=0;k itemcount++;
itemcount2++;

sysmessage(s, "You reach down and pick some cotton.");

Add this line just before 'int k;':
items[itemcount].priv=items[itemcount].priv|0x01;