55 



As the flower matures the anther-point recurves (fig. 1, 

 pi. vii.), exposing tlie caudicle and upper portions of the pollen- 

 masses to the drying effects of the atmosphere. As a conse- 

 quence the caudicle begins to curl upwards, dragging the 

 pollinia with it and leaving a triangular space between itself 

 and the back of the rostellum. This is the first stage of the 

 complete rotation of the pollinia which subsequently occurs, 

 unless they are removed. They can be readily detached by a 

 needle passed into the triangular space just referred to at the 

 back of the rostellum. This is probably what happens when 

 removed by crawling insects. In a very large number of flowers 

 examined I found that the pollinia had been removed and in 

 many cases pollen-masses, completely detached from the 

 rostellum, were seen adhering to stigmas. In some of these 

 cases the pollinia were still attached to the rostellum, showing 

 clearly that the masses on the stigma had been transported 

 from other flowers. Hence it is certain that cross-pollination 

 does occur in a large percentage of cases in this species. 

 Whether the agent is always Trogoderma adelaidce I am not 

 prepared to say. It is, however, the only insect visiting these 

 plants to which I have seen pollen-masses adhering. 



Should the pollinia not be removed, the act of rotation 

 is proceeded with. The second stage of this is shown in fig. 2, 

 where the pollinia have assumed a position at right angles to 

 the back of the column. The third stage is shown in fig. 3. 

 The curling of the caudicle has proceeded to such an extent 

 that the two masses are raised vertically above the rostellum. 

 Finally they are deposited, usually with great accuracy, on 

 the middle of the stigmatic surface (fig. 4). When this occurs 

 the caudicle still remains attached by the disc to the rostellum. 



Occasionally, from some accidental cause, the curling of 

 the caudicle in the final stage of rotation is irregular, and there 

 is a tendency for the masses to be deposited elsewhere than 

 on the stigma. This is generally prevented, however, by the 

 lateral appendages, which are higher than represented in 

 figs. 4 and 5. Such a misplacement is shown in fig. 5, where 

 the lateral appendage has saved the situation, and pollination 

 has been successfully effected. 



The fertilization of Prasophyllum gracile then is one of 

 extreme interest. It is an instance where cross-pollination is 

 clearly invited, but failing this the plant is able to accomplish 

 the process of fertilization by itself. 



Whether this method of pollination takes place in other 

 species of Prasophyllum I am not at present in a position to 

 say, but judging from the extreme degree of rotation so fre- 

 quently seen in the pollinia of plants of this genus, it probably 

 does, though perhaps not so frequently as in the species under 

 review. 



