Cheeseman. — On the Fertilization of Tlielymitra. 293 



At its base it is thick and fleshy, but it becomes thin and membranous 

 towards the sides and two-lobed summit. The rostellum is lodged between 

 the terminal forks of the stigma, in front of which it projects as a rounded 

 boss. When mature, it consists entirely of viscid matter, covered with 

 an extremely deHcate membrane. At this stage its connection with the 

 stigma is easily ruptured, so that it can be readily removed by a slight 

 touch. 



The anther attains its full size and development while the flower is yet 

 in the bud, and long before expansion each cell splits down its outer face, 

 exposing the pollinia. As these rest immediately behind the rostellum, and 

 in contact, or nearly so, with its viscid posterior surface, they invariably 

 become firmly attached to it. After this takes place, the column lengthens 

 considerably, thus causing the anther to occupy a higher position relatively 

 to the stigma and rostellum than before. As the pollinia have become 

 affixed to the rostellum, they cannot accompany the anther in this move- 

 ment, and the anther-case being dragged from them they remain hanging 

 to the back of the rostellum in the narrow passage existing between the 

 stigma and column ; the upper part of the pollinia slightly overtopping the 

 stigma. This is the state of things just before the expansion of the flower. 



In fine sunshiny weather the flowers usually open about nine o'clock in 

 the morning, neatly reclosing about four or five in the afternoon. There is, 

 however, considerable irregularity as to this, some varieties only opening 

 for a short time in the middle of the day, others remaining expanded for a 

 much longer period. In cloudy or showery weather the flowers never 

 expand so fully as on a clear day. In stormy or very wet weather they 

 generally do not open at all. I have observed that when rain has obtained 

 access into the flower the pollinia are frequently washed into a pulpy mass 

 at the bottom of the recess behind the stigma ; so that there can be no 

 doubt that the closing of the flower acts primarily as a protection for the 

 pollen against rain or dew ; although in some of the varieties it certainly 

 seems to be carried further than is required for this purpose. The flowers 

 are quite scentless, and I have never observed that any nectar is secreted. 



If a newly-expanded flower is taken and a blunt needle inserted in such 

 a manner that the front of the rostellum is touched, the viscid matter com- 

 posing this organ at once adheres to the needle, and if it is withdrawn, 

 taking care to move the point in an upward and forward direction, the ros- 

 tellum, with its attached pollinia, cannot fail to be brought away with it. 

 This experiment should only be tried with flowers that have recently ex- 

 panded, for, from reasons that will become apparent further on, the pollinia 

 can only be removed with certainty immediately after the flower first opens. 



So far, the whole structure of the flower seems designed to favour cross- 



