Under the selection pressure of crude toxin filtration, three kinds of treatment methods and four kinds of phytotoxin concentrations were used to screen the blast-resistant callus phenylalanine.
" How're you doing, Harry? " said the nearer of the two, grinning at him and holding out a large hand, which Harry shook, feeling calluses and blisters under his fingers.
This hand was rough from work, brown with sunburn, splotched with freckles. The nails were broken and irregular, there were heavy calluses on the cushions of the palm, a half-healed blister on the thumb.