SUPPLEMENT 



Franseria are examples. In other species, the ripened akenes are 

 held within the persistent involucre, just as seeds are contained in 

 capsules, until the wind is strong enough to scatter them. The 

 fruits of Umbelliferse have much of their stored food in the form 

 of oil, and so are rather buoyant : besides this, they have frequently 

 thin margins or wings. Other genera have their fruits covered with 

 hooked spines. 



But it is when we consider the pollination of the flowers, that the 

 advantages of their close association are apparent. Solitary flowers 

 may develop individuality, and succeed in attracting the most desir- 

 able of guests, but nature's preference for the more social method is 

 evidenced by the fact that ninety per cent of all flowering plants have 

 their flowers in clusters. We are told that the two orders discussed 

 in this chapter exceed all others both in the number and variety of 

 their guests. Insects with long tongues rarely frequent the Umbel- 

 liferae, but the honey of the Composite, since it is at the base of 

 extremely slender tubes, rising only occasionally so as to be visible in 

 the throat, is reserved for butterflies and bees. The pollen of both 

 orders is abundant, and is gathered by many species of insects. 



These orders generally provide for both cross and close pollination. 

 The clusters of many Umbelliferse are, like the sanicle, in their first 

 stages, practically pistillate, and hence invite cross pollination, but 

 the very viscid stigmas do not wither until the anthers of neighbor- 

 ing flowers begin dehiscence; in most cases, the styles diverge and 

 the stigmas apply themselves to their neighbors' pollen. The fennel, 

 in later stages, sends up its staminate umbellets above those with 

 still receptive stigmas, so that pollen falls on them. A large number 

 of Umbelliferae have many staminate flowers mingled with the per- 

 fect ones. Most Compositae show a preference for pollination from 

 one head to another. In some cases the plants are actually dioacious; 

 frequently the ray flowers are pistillate and mature some time before 

 the disc flowers of the same head; sometimes all the flowers of a head 

 are in the pistillate stage for a time, and finally all are staminate, but 

 the condition of the sunflower is the most common, that is, there is a 

 shifting ring of flowers in the pistillate stage surrounding those that 

 are shedding pollen. The flowers can usually get pollen from their 

 neighbors in the same head; their guests bring it, or they may 

 stretch out their style branches and reach it, or they are pollinated 

 by the closing of the heads, or perhaps the receptacle is convex and 

 the pollen falls from the younger central flowers upon the stigmas of 

 older ones. Besides this pollination from neighbors, self pollination 

 is not rare; as the style branches separate and coil back, the inner, 



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