4 8o BOTANICAL GAZETTE [juxe 



He was able to induce premature fading by applying most various substances 

 to the stigma: besides their own living pollen, volcanic river-sand, spittle, dead 

 pollen and pollen extract, dead and leached pollen of the same species or of 

 other genera or even of other and remote groups, and extract of gynostemium 

 tissues induced it, and apparently also 5 per cent, saccharose. He was not able 



arViQt th(> rVipmiral aorpnt nr flprpnts were, in these reactions. Wound- 



■rmme 



ing the stigma or the tissue at the apex of the gynostemium also caused premature 

 fading. Closure of the stigma and swelling of the gynostemium could be effected 

 by bestrewing the stigma with living or dead pollen of orchids (any genus) or 

 even of Hibiscus, and with the alcoholic extract of pollen. On the contrary, dead 

 pollen and pollen extract had no effect or the very slightest in inducing swelling 

 of the ovary, which occurred only when living pollen germinated on the stigma 

 and its tubes grew into the ovary. The greening of the perianth (peculiar to 

 certain species) appears only when the ovary has previously begun to swell and 

 to turn green. 



Fitting considers fading as the end process of floral development, simply 

 released by the pollen stimulus or others earlier than it is autonomously. The 

 stimulus, however, does not merely hasten development; it diverts its course, 

 for a perianth half open and quite incompletely developed may be made to fade 

 in twelve to twentv-four hours bv a stimulus which proceeds from the distant 



stigma. This also offers a new example of the separation of perceptive and 



reactive regions. The closure of the stigma, etc., appears to be strictly a case 

 of chemomorphosis, but the agent does not produce any effect on the ovary, 



whose growth and formation of ovules, and so the consequent greening ot the 

 perianth, depend on the penetration of the pollen tube; but whether the stimulus 

 is mechanical or chemical does not appear. 



The prompt fading of the flowers, possible after an insect bite on the stigma 

 or after stimulation by foreign pollen, and the small crop of fruit on these tropical 

 orchids, awaken doubts in Fitting's mind as to the validity of the teleological 

 interpretation of the elaborate mechanisms which are believed to secure cross- 

 pollination. Perhaps they were effective in a past age when insect life was 

 richer, he adds by way of apology for his temerity in suggesting such heresy. 

 He will find this heresy not unwelcome, we imagine, in this country, where ecolo- 

 gists are questioning whether there is even adequate proof that cross-pollination 

 is advantageous. — C. R. B. 



■^ 



Cytology of Oenothera. — Geerts 23 published an account of embryo-sac 

 development and chromosome reduction in Oenothera. A row of four mega- 



formed 



rmin 



J the embryo sac. Its nucleus divides only twice. Both 



*3 Geerts, J. M., Beitrage zur Kenntnis der cytologischen Entwicklung von 

 Oenothera Lamarckiana. Ber. Deutsch. Bot. Gesells. 26a:6o8-6i4. 1908. 



, Beitrage zur Kenntnis der Cytologic und der partiellen Sterihtat von 



Oenothera Lamarckiana. Separate (source unknown), pp. 116. pis. 5-22. 190c;. 



I 





