1893.] Mr Willis, On Oynodioecism. 129 



its effects in diminishing the liquefying (i.e. enzyme action) 

 power of certain forms, and even in altering their mode of 

 growth, so that the aspect of the colonies on gelatine plates is 

 affected. 



These changes in aspect are not a mere matter of preventing 

 or increasing the production of pigment, &c., but are due to 

 effects on the growth of the colonies. As regards pigments, the 

 author has examined a pigment of one of these river-species, 

 which pigment, though so resistent as to bear solution in alcohol, 

 evaporation and drying at 100° C, and re-solution, without appa- 

 rent alteration, is destroyed in an hour or two on exposure to 

 light. 



(2) On Oynodioecism (third paper), tvitli a preliminary note 

 upon the origin of this and similar phenomena. By J. C. WiLLiS, 

 M.A., Gonville and Gains College. 



The experiments begun in 1890, upon which two preliminary 

 notes have been published (Proc. Gamb. Phil. Soc, vii. 1892, 

 p. 348, and viii. 1892, p. 17) have been continued during 1893. 

 The chief point of immediate interest in the present year's ob- 

 servations was the change of type of some plants. It has hitherto 

 been taken for granted, so far as can be found from a careful 

 study of the literature, that a "female" plant remains female 

 throughout its life history, and a hermaphrodite likewise. This 

 year's experiments have shown that this is not the case. A wild 

 female plant of Origanum vulgare which was transplanted from 

 Abington (see 2nd paper, p. 18) and which remained female 

 during last year, came out hermaphrodite in the present season. 

 On July 15, 1893, it was in full flower, and was covered with 

 normal hermaphrodite flowers, with here and there a stray female 

 flower, just like a normal hermaphrodite plant. The few female 

 flowers were almost entirely borne on the lower lateral tufts. 

 On July 22, it was in a similar condition, and the female flowers 

 were comparatively large. Presently, however, a change occurred, 

 and by Aug. 10, the plant looked like a normal female, only 

 bearing a few hermaphrodite flowers. (The flower of Origanum 

 usually lasts about a week.) In this condition it remained for 

 the rest of the season, at times, however, bearing a considerable 

 number of hermaphrodite flowers. 



The bed of seedlings of 1890 (see 2nd paper, p. 18) flowered 

 vigorously again this year ; but although in 1892 there were 

 several female plants among them, during this year no stalks 

 appeared which could be termed female, though some of the 

 hermaphrodites bore several female flowers. As the female plants 

 of 1892 were not specially marked, it was impossible to determine 

 whether they had turned into hermaphrodites, but in view of 



VOL. VIII. PT. III. 10 



