Abstract
In the previous report**, the mote formation of cotton seeds has deen classified into following 3 types : (i) the ovule itself was defective, lacking in embryosac formation; (ii) the ovule was normally formed, but the pollen-tube, although reaching to ovule, failed in completing the fertilization; (iii) the fertilization was normally functioned, but the successive development of ovule was arrested. In the present paper, further investgation was added to get the actual frequencies of above mentioned 3 types. Using one variety of each upland and Chinese cotton, embryonal development was traced at each stage of 7, 10 and, 15 days after flowering and at maturation. Formaline acetic alcohol was used for fixation, and longitudinal sections of 10 to 15μ thick were stained with DEL-AFIELD'S haematoxylin. It was determined that the non-fertilized motes, wherein the above No.1 and No.2 types are included, were almost constant in their frequency throughout the various stages, meanwhile the fertilized motes, that is the type No. 3, increased gradually in number as showh in Table 2. Therefore, the increasing occurrence of motes shown in Table 1 should be due to the latter case. When the non-fertilized motes are divided into the types, No. 1 and No. 2, each may play some role but be of rather less importance in formation of motes, because the frequency of each one is merely less than 3 percent respectively as shown in Table 3. As to the embryonal development of fertilized motes, when observed in comparison with the normally growing ovules, following facts were confirmed (Table 4, 5, 6). 1. The fertilized motes begin to occur from an earlier stage, and the majority of them are observed before 15 days after flowering. 2. Some of fertilized motes are arrested in their development immediately after fertilization, and are deformed into tiny structure. The others continue to develop slowly for a while, but cease to grow soon or late, and remain as they are in mature bolls,
