▁of ▁their ▁host ▁plant . ▁The ▁mine ▁has ▁the ▁form ▁of ▁a ▁simple ▁gallery ▁throughout , ▁and ▁is ▁verm iform ▁in ▁character , ▁the ▁loops ▁being ▁very ▁closely ▁applied ▁to ▁one ▁another , ▁but ▁never ▁crossing . ▁As ▁a ▁rule ▁the ▁gallery ▁at ▁first ▁wind s ▁backwards ▁and ▁for wards ▁in ▁slightly ▁increasing ▁distances , ▁closely ▁applied ▁to ▁itself , ▁and ▁in ▁a ▁direction ▁more ▁or ▁less ▁parallel ▁to ▁the ▁long ▁axis ▁of ▁the ▁leaf . ▁Then ▁it ▁changes ▁its ▁direction ▁for ▁one ▁almost ▁at ▁right ▁angles ▁to ▁the ▁earlier ▁one , ▁now ▁crossing ▁the ▁leaf ▁in ▁cur ved ▁swe eps ▁from ▁edge ▁to ▁mid rib , ▁this ▁latter ▁forming ▁a ▁certain ▁obst acle ▁to ▁tres pass ▁on ▁the ▁other ▁half ▁of ▁the ▁leaf . ▁On ▁reaching ▁the ▁upper ▁region ▁of ▁the ▁leaf ▁the ▁mine ▁becomes ▁less ▁verm iform ▁in ▁character ▁and ▁becomes ▁rather ▁tort uous ▁in ▁its ▁direction , ▁crossing ▁the ▁mid rib ▁in ▁its ▁upper ▁and ▁th inner ▁part , ▁and ▁continu ing ▁down ▁the ▁other ▁half ▁of ▁the ▁leaf ▁in ▁more ▁or ▁less ▁close ▁proxim ity ▁to ▁the ▁mid rib ▁or ▁outer ▁margin . ▁This ▁latter ▁portion ▁of ▁the ▁mine ▁is ▁often ▁deeper ▁in ▁the ▁leaf ▁than ▁the ▁earlier ▁part . ▁The ▁entire ▁mine ▁is ▁in ▁the ▁upper ▁surface ▁of ▁the ▁leaf , ▁and ▁no ▁trace ▁of ▁it ▁can ▁be ▁seen ▁beneath . ▁The ▁colour ▁of ▁the ▁mine ▁is ▁a ▁pal er ▁green ▁than ▁other ▁port ions ▁of ▁the ▁leaf . ▁The ▁terminal ▁portion ▁of ▁the ▁gallery ▁may ▁be ▁slightly