There are 7 words that start with 'megasp'.
| megaspore | megaspores | 
| megasporic | megasporangia | 
| megasporangium | megasporophyll | 
| megasporophylls | |
Note: These 7 words that start with 'megasp' are found from the USA & Canada version of the tournament Scrabble word list.