ABSTRACT
<p><b>OBJECTIVE</b>To observe and study the correctness of the proposition dicot have free vein termination but monocot have not. To evaluate the reliability of the identification principle that is based on above proposition.</p><p><b>METHOD</b>Fourteen species of pharmaceutical monocot come from 9 families and 3 species of pharmaceutical dicot come from 3 families were observed by using the method of microscopic identification.</p><p><b>RESULT</b>The free vein termination existed in the vein-islets of 10 species of monocot from 8 families, Zingiberaceae, Stemonaceae, Gramineae, Liliaceae, Orchidaceae, Alismataceae, Dioscoreaceae and Araceae ect, and it was not to find the free vein termination in monocot Iris tectorum, Belamcanda chinensis (Fam. Iridaceae) and Imperata cylindrica, Coix lacryma-jobi (Fam. Gramineae). Three species dicot, Cinnamomum burmannii, Castanea mollissima, Mangifera indica, all had the free vein termination. The free vein termination of C. burnmannii was sparse, and C. mollissima's was usually covered by non-glandular hair.</p><p><b>CONCLUSION</b>The proposition is not universally applicable, monocot have no free vein termination. The identification principle is unreliable, which distinguish between medicinal dicot and monocot leaves according to whether the free vein termination exists or not.</p>