100 THE VICTORIAN NATURALIST. 



If there is no wind or if the air is close and damp, the ejection of 

 pollen is postponed until the atmosphere has again become dry. 



In another group of plants the anthers are borne on long 

 filaments, and are set oscillating and vibrating by the least breath 

 of wind, the pollen being in consequence discharged in little 

 pinches. The flowers of this kind contain pistils as well as 

 stamens, but they are dichogamous, and the pollen dust must 

 be transported to other flowers which happen to be at a younger 

 stage ot development. 



Prominent among the plants belonging to the first-mentioned 

 category stand the grasses and sedges. With these temperature 

 and the hygroscopic condition of the air in particular play an 

 important part. The most favourable conditions for pollination 

 in the case of most grasses prevail in the early morning, when the 

 first rays of sunshine fall upon the flowers, and the temperature is 

 rising gently. Under such conditions pollination is accomplished 

 with astonishing rapidity. In some cases the glumes spring open, 

 the stamens grow out, the anthers open, and the pollen is 

 scattered all in the space of a few minutes. 



In all the cases discussed hitherto the pollen escapes from the 

 place where it originates into the air direct ; but there is also a 

 large number of plants whose pollen falls, in the first instance, on 

 to some spot within the province of the flowers where it is pro- 

 tected from becoming wet, and in which it remains a period ot 

 varying duration. Very different parts of a flower are utilized in 

 this manner as temporary halting-places for the pollen. The 

 temporary deposition of the pollen on the backs of the flowers is 

 common to all the numerous trees and shrubs which have their 

 male flowers aggregated in pendant catkins or spikes, resembling 

 tassels or fringes in appearance. The floral spikes of all these 

 plants are erected at first, and in the form of short sticks, cones, 

 or cylinders. A short time before the anthers burst the axis of 

 the spike elongates and becomes pendant. The back of each 

 flower is so contrived as to catch the pollen falling from the 

 set anthers of the flowers above it, and retain it until the tassels are 

 swinging by the wind, and the pollen is, in consequence, distributed. 



A close connection exists between these various contrivances 

 to ensure that pollination shall only take place at the best 

 possible moments, and the maintenance of a free passage in the 

 direction in which the pollen is to be transported by the wind, 

 and, further, between these adaptations and the shape of the 

 stigmas devised for the reception of the pollen. It is obvious 

 that no barrier must be interposed in the path of the little clouds 

 of pollen dust on their journey to the stigmas. On this account, 

 also, all flowers which have the pollen blown out of them by the 

 wind are arranged in spikes and panicles, and project freely into 

 the air, and are never clothed with a mass of foliage. 



Particular attention may be drawn to the fact that a large 



