REPROD UCTION. 233 



apple-fruit (pome) may be considered as a stone-berry with a thin 

 pergament-like endocarp (RADLKOFER, WARMING). 



5. Berries. The entire pericarp is soft and fleshy, or leathery 

 at the outer part (grape, tomato, orange). 



(The foregoing description of fruit - forms is according to 

 THOME.) 



There are many structural arrangements to facilitate the distri- 

 bution of seeds and fruits. Although the physiological factors 

 were not considered in the description of fruit-forms, we must not 

 for a moment forget that such factors nevertheless exist, some 

 of which have been carefully worked out, while others require 

 further elucidation. In 1873 HILDEBRAND published his com- 

 munication on the Distribution of Seeds by Plants, to which 

 I refer the student, and from which the following statements are 

 taken. 



The following peculiarities of seeds and fruits facilitate their 

 distribution by air-currents. 



1 . Reduced size of seeds (including the spores of cryptogams) ; 

 lightness of seeds (orchids). 



2. Flat form of seeds (Lilium, Tulipa) ; wing-like appendages 

 (conifers, many crucifers). 



3. Wing-like appendages of fruits ( Ulmus, Fraxinus, Betula, 

 Acer, Rheum, Isatis) ; the winged appendages may also be formed 

 by modified bracts (linden, hawthorn), or by the perianth (Salsola). 



4. Hair-like appendages to seeds (Epilobium, Salix, Gossy- 

 pium). 



5. Hair-like and feather-like appendages to fruits (Anemone, 

 Composite^). 



(The following figures will assist in explaining fruit-forms as 

 well as the appendages just referred to.) 



We must also mention the arillus or seed-mantle with which 

 many seeds are equipped. It may develop from the funiculus, the 

 hilum, or the micropyle. In the seeds of Evonymus europcea it 

 is of a yellowish-red color ; in seeds of Taxus it is well developed 

 and red in color. Such highly colored formations attract animals, 

 especially birds, which feed upon the seed. Other structural 

 arrangements for the successful distribution of seeds are the thick 

 and hard seed-coverings (testa), which resist the digestive action of 

 the juices of the stomach and intestines of animals. Animals, 



