46 



8. Fruit : 



Sometime after pollination the egg cell or ovule is fertilized, and 

 as a result of fertilization, the ovule, together with the surround- ' 

 ing ovary, enlarges. The enlarged ovules, together with inclosing 

 ovary, form what is termed the fruit. The fruit may in addition 

 comprise modifications of other organs intimately connected with 

 the ovary. • 



Seeds are products of the flower and are usually regarded as 

 reproductive organs, but in reality they are the result of reproduc- 

 tion. Their chief work is the dissemination and the protection of the 

 offspring of reproduction. They are usually covered by hard and 

 impermeable coats which protect the young plant contained within 

 from the many dangers with which it is beset. Nature tries to 

 guard against these dangers by developing suitable protective cover- 

 ings for each species. Nature, however, is not always satisfied by 

 simply developing a thick and impermeable coat, but in addition it 

 develops an internal tissue which is compact and contains little 

 water. If a seed possess these essentials it is well protected against 

 most of the destructive agencies to which it is exposed. The chief 

 dangers to which seeds are subject are premature germination, loss 

 of vitality, and destruction by animals. Each seed usually has a 

 suitable covering which regulates the germination in spring. This 

 regulation is necessary so as not to allow the tender plant to emerge 

 before the external growth conditions are favorable for its develop- 

 ment. An embryo within a thin-coated seed would often be stimu- 

 lated by a few warm days in spring with the consequence that the 

 resulting tender plants would be killed by later frost. Nature acts 

 as a guardian and places a thick coat around such embryos, and as 

 a result they are not stimulated until later when frost danger is 

 past. 



Food is stored in various plant organs such as roots, stem, and 

 branches, and is usually most abundant and conspicuous in the 

 seeds. It occurs in various forms and may often differ in composi- 

 tion. Food stored in the seed is very valuable because it supplies 

 nourishment to the small and tender plants before they have de- 

 veloped the roots with which they draw nourishment from the soil 

 and supply water to the leaves where starch and sugar are manu- 

 factured. Primitive man obtained considerable food from the seeds 

 of trees, and present man derives certain foods for himself and his 

 animals from some of our common trees. The food value of seeds! 

 varies with the species. Some species like the Willows contain very 

 little food, while others like the Chestnut are rich in food. 



The time at which the fruit matures varies with the species. Wil- 

 lows, Poplars, and Elms mature their fruits in spring; others, like 



I 



