462 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



containing a complete list of his crosses in the Paphio- 

 pedium group of Cypripediums from 1892 up to August 31, 

 1897. On referring to this I find that Cypripedium barbatum 

 has been used twenty-two times as a seed parent, and has been 

 crossed nearly the year round from December to September. 

 In these twenty-two instances there was an extreme difference 

 between the longest and shortest period of ripening ( from pol- 

 lination onwards) of 149 days, or about five months, the longest 

 time being 315 days, or ten-and-a-half months, and the shortest 

 period 166 days, or five-and-a-half months ; so that the differ- 

 ence between the longest and the shortest was nearly as much as 

 the whole time of the shortest period. A further examination of 

 the facts and figures points to the conclusion that one of the 

 chief causes of the extreme difference lies in the season of the 

 year the cross was made, for the pod which ripened quickest was 

 pollinated on June 24 ; while that which ripened slowest was 

 pollinated on December 8 ; and between December and June, 

 with a slight exception or two, there was a gradual shortening of 

 the period of ripening, and from June to December a marked 

 lengthening of that period. The average period of ripening for 

 each month was as follows : — 



December, 315 days; March, 234 days; April, 209 days ; 

 May, 216 days ; June, 187 days ; August, 210 days ; September, 

 287 days. Thus it seems that the nearer to Midsummer the 

 flower was pollinated the quicker the pod ripened, and the 

 nearer to Christmas the slower the pod ripened ; and I think 

 that there can be little doubt that this was due to the influence of 

 the sun at those different periods. Further it may be noted that 

 the pod which ripened slowest was formed and matured between 

 December 8 and October 19 of the following year ; while the 

 pod which ripened quickest was formed and matured between 

 June 24 and December 7 of the same year. This seems to 

 suggest that the power of the sun is more essential in the early 

 stages of formation than at any other time. We have already 

 seen from Dr. Hildebrandt's observations that in Cypripediums 

 some four months elapse between pollination and actual fertili- 

 sation, so that we may reasonably conclude that the growth of 

 the pollen tubes, and the consequent fertilisation of the ovules, is 

 considerably hastened by the power of the sun ; and I hope our 

 Italian friends will make use of the golden opportunities of 

 sunny Italy. 



