Try to make your search as simple as possible:
Ech. will find all items including that sequence of letters.
Search results for "Ech.":
"Ech. caespitosus" - Echinocereus reichenbachii ssp. perbellus Ellis Co
"Ech. cinerascens v. tulensis" - Echinocereus cinerascens Tula Tam.
"Ech. coccineus v. gurneyi E NM" - Echinocereus triglochidiatus v. gurneyi Elk NM