(1) The somatic number of chromosomes of the genus Lilium are determined in the present study as follows; 2n=24, L. philippinepse var. formosanum, L. avratam., L. auratum var. hamaonum, L. davuricum, L. davuricum var. venustwm, L. davuricvm subsp. Thunbergianum, L. concolor var. pulchellum f. miniatum, L. concolor var. pulchellum, f. partheneion, L. concolor var. pulchellum f. coridion, L. speciosum, L. speciosum f. rubrum, L. speciosum var. tairnetomo, L. Henryi, L. amabile, L. cernuum, L. medeoloides. 2n=26, L. japonicum. 2n=86, L. tigrinum var. flore-pleno. (2) In the root-tip cells of L. tigrinum var. flore-pleno 36 chromosomes were invariably counted, 6 of which were larger among them 3 have median fiber-attachment and the other have submedian. The remaining 30 shorter chromosomes are of either the terminal or sub-terminal class. This plant is probably the triploid form as L. tiyrinum.(3) The number 26 of L. japonicum is a new number among those found in the genus Lilimn, there being a pair of markedly small chromosomes. These small chromosomes are probably the fragments formed as a result of segmentation at the points of transverse sulture or constriction. (4) The length of chromosomes was measured in L. philippinense var. formosanum, L. japonicum and L. speciosum; it was confirmed that in these species there is always a constant length difference among the chromosomes. (5) From the result of calculation nearly the same total value of the sum of chromosomes lengths was obtained and the relative length of chromosomes to the total sum of the chromosome lengths shows no significant difference in corresponding chromosomes among these species. These results may throw light on the phylogenetic relation between the species from the view point of chromosome morphology. For part of the materials used and for the helpful interest and advice thoughout.the course of the work, the writer is imdebted to Dr. Y. SiNOTÔ under whose direction the investigation has been carried on.