401 



The authors point out at wliat irrofjul.ir intervals tlio flower- 

 ing occurs : and they enll attention to the way in wlii(;h the dates 

 differ from place to place, as for instance March the first may be 

 the day for flowers in one s))ot, hut thirty miles away the day for 

 flowers may be March the fourth. The authors then draw the de- 

 duction that flowering has not a fixed period, hut depends on 

 external circnmstances, which circumstances have to be identified. 



For the purpose of their work a large number of plants were 

 fixed in positions in the Buitenzorg Gardens where they obtained 

 very different amounts of light: those that got the least then 

 flowered the less freely, but they nevertheless flowered on the same 

 days as their more favoured neighbours. The sums of the light and 

 direct heat of the sun, therefore, are not the controlling factors 

 for the opening of the flowers : they act only upon the vigour of 

 the plants. 



Plants in the Utrecht Gardens did not flower through the 

 winter, over which the temperature in the plant houses was con- 

 trolled by artificial heat within narrow limits : l)ut when spring 

 brought bright weather and the sun shone strongly on the glass 

 roofs it was impossilde to keep the temperature any longer from 

 rising far above its former limit, and then in three weeks the plants 

 l)urst into flower, not only at Utrecht, but at Hamburg and Bonn, 

 the bright spell spreading over all three places, as if the rise in 

 temperature or quite possibly the greater fluctuations had iriveu the 

 required stimnlns. 



Further the authors do not go than to make a suggestion that 

 this is so and to add that very probably moisture also has an in- 

 fluence : because the flowering takes place so irregularly they suggest 

 that it is possible that the two work together. 



If a Pigeon Orchid plant be examined it will be seen that the 

 flowers are produced from large persistent scaly buds. The authors 

 compare these l)uds to the winterbuds of Euroi)ean trees, calling 

 attention to the circumstance that winter buds are formed in the 

 autunm to pass throngh a period of rest until spring brings a 

 stimulus for renewal of growth ; and they bring forward observa- 

 tions to show that a period of retarded growth occurs in the 

 maturing of the flowers in the Orchid followed by extremely rapid 

 growth at the end, the flower buds rushing to the expanding. 

 During this time of slow growth many buds may fail : the others 

 arrive at a certain stage and wait : the longer tlie requisite stimulus 

 is in coming the more buds should there be all brought together to 

 tlie same stage, and the more abundant should be the flowering when 

 it comes, only there is this death of buds to interfere with the 

 process. When the stimulus comes all the buds wliich have reached 

 the stage of arrest find themselves driven forward together to the 

 flowering, and so it is synchronised. 



It is evident that much remains yet to be ascertained before 

 we have a complete understanding of the phenomenon: l)ut the 

 hy])ot]iesis which Drs. Putgers and Went put forward appears to 

 offer a ]:oint of vantage from which new e\])eriments nuiy l)e 

 directed, and may be examined briefly in regard to nbservalions 

 made in Sinaaiiore. 



