In his Bliithendiagramme, the work which can never be sufficiently praised, E i c h 1 e r gives a set of definitions of the four types of monochasia, with explanations of them, all of the highest value. I should therefore have had no reason to treat the topic here, if the study of the inflorescence of the Plumbaginaceae (6) had not furnished some observations which might give further information on a point which hitherto had remained doubtful.