527 



peciilicarities are so striking, that the plant has even received 

 a Dutch name and is known in Java as "duifjes", in Singapore as 

 "pigeon orchid". Tiiis name retei'S io tiie white flowers of a size 

 of about 3 centimetres, wlucli appear simultaneously on many 

 plants and aie all the more noticeable, because thej' remain open 

 only for a single day. Everywhere hundreds of these small, white 

 flowers are seen, wliich are, moreover, delicately scented. Next day 

 the phenomenon is over and only after several weeks, or even 

 months, the "pigeon orchids" again suddenly appear in full bloom ; 

 next day only faded flowers can be found. 



We have now studied the phenomenon in question with plants 

 in their native habitat and with others, sent to Utrecht, wliich weie 

 finally cultivated there in two different glass houses. A few results, 

 obtained by us in this manner, are briefly communicated here ; for 

 further details we refer to a fuller paper, which will soon be published 

 elsewhere. We wish to emphasize, that we have not succeeded in 

 solving the problem completely, but nevertheless our observations 

 appear sufficient to deprive the phenomenon of its air of mystery. 



In the first place we found tliat the interval between two succes- 

 sive flowering periods is subject to considerable variation ; at Buiten- 

 zorg minima of 4 and 10 days, and a maximum of 94 days were 

 observed, but in Utrecht the intervals were generally much longer, 

 while in winter flowering cannot be observed at all. 



Furthermore it became very evident, that external conditions 

 influence the outset of the flowering. Accordingly the lime varies in 

 the East Indies from place to i)lace, and only coincides occasionally 

 for neighbouring places, such as Meester Coriielis, Weltevreden and 

 Menes (March 14''' 1913) or Maos, Klampok and Bandjarnegara 

 (March 26''' 1913\ Likewise the time of flowering often differed at 

 Utrecht in the two glass houses, in which temperature and humidity 

 were not ke[)t equal ; on the other hand the flowering period in 

 spring was once found to synchronize in glass houses at Utrecht, 

 Bonn and Hamburg. 



When plants, previously grown at a spot A, and hence having 

 definite flowering days, are transferred to a spot B, they acquire 

 another flowering time, which is identical with that of plants grown 

 at B from the beginning. . This was found on transporting plants 

 from various parts of Java and from Deli to Buitenzorg and con- 

 versely on moving plants from Buitenzorg to Medan. The same 

 change was observed in plants sent from the tropics to the hothouses 

 of European botanic gardens. 



With respect to the question, what external factors play a part 



