Prothali or Prothalli: How To spell?
The word Prothali is misspelled against Prothalli, which is plural of "Prothallus"
Prothalli has double "ll" is mispronounced as "l"Remember double 'LL' in between the strings protha & i which should not be misspelled with single 'L'
Wrong Spelling:  protha-l-i  Correct Spelling:  protha-ll-i 
Find more incorrect spellings of Prothalli to spell right way.