IRISES FOR THE ROCK-GARDEN AND THE WATERSIDE. 457 



Phenological Observations. 



Some notes have been kept of the extreme dates of flowering of the 

 various species ; they extend over a number of years, and serve to show 

 what a wide range many Irises have, and how we may have Iris flowers 

 continuously for about eight months in each year. 



Only a few examples will be quoted now. 



Iris Vartani. 

 His t rio . 



Kaempferi 





stylosa . 



. January 



1 „ April 22 



>> 



Rakeviaixa 



5> 



19 „ March 20 



« 





?> 



21 „ „ 7 



>> 



DaixjordicB 



>> 



27 „ „ 5 



>J 



J.\.l VviMI&v 



. February 



1 „ April 7 



>> 







6 „ „ 25 





tuber osa 





23 „ „ 25 



>> 



caucasica 



. March 



22 „ „ 25 



J> 



lacustris (fig. 138) 



April and May, and again in Augus 



it 



' Pumila ' group . 



. April 



15 to May 30 



» 



1 Germanica ' group 



. May 



3 „ July 8 



>> 



Leichtlini 





6 „ May 19 



» 



susiana 





22 „ „ 30 





Korolkoici 





23 „ June 8 



if 



1 Sibirica ' group . 





26 „ July 7 



>> 



virginica 





31 „ „ 6 



>> 



Boissieri 



. June 



3 „ June 24 



>> 



Xvphium 



)> 



10 „ July 7 



>> 



Pseudacorus . 





11 „ „ 10 



»> 



ochroleuca . 



>> 



12 „ „ 8 





xiphioides 



>> 



18 „ „ 14 



December 13 to January 16 

 31 „ February 26 



. during July and August. 



The duration of each flower varies from one day only in Iris arenaria, 

 three to five days in the Flag Irises and the greater number of species, 

 to seven to ten days in the early bulbous kinds. In Iris reticulata the 

 earlier flowers have a markedly longer duration than the later ones, which 

 come perhaps for five or six weeks in succession ; this is probably due to 

 the paucity of insects in early spring retarding pollination, and may also 

 be partly due to slower life from the lower temperature and lesser sun- 

 power. 



