46 DEFINITION AND CLASSIFICATION OF FRUITS. 



2. REPRODUCTION BY MEANS OF FRUITS. 



Definition and Classification of Fruits.— Fertilization and Fruit-formation in Cryptogams.— The 

 Commencement of the Phanerogamic Fruit. — Stamens.— Pollen. — Arrangements for the Protec- 

 tion of the Pollen.— Dispersion of Pollen by the Wind. — Dispersion of Pollen by Animals. — 

 Allurements of Animals with a view to the Dispersion of Pollen.— The Colours of Flowers 

 considered as a means of attracting Animals. — The Scent of Flowers considered as a means of 

 attracting Animals.— Opening of the Passage to the Interior of the Flower.— Reception of 

 flower-seeking Animals at the entrance to the Flower. — Taking up the Pollen. — Dispersion of 

 the Pollen. — Cross- pollination. — Autogamy. — Fertilization and Fruit-formation in Phanerogams. 



DEFINITION AND CLASSIFICATION OF FEUITS. 



To all appearance there is no difference between the protoplasts which develop 

 into brood-bodies and those which are the points of origin of fruits. Nevertheless, 

 it has been ascertained by experience that the protoplast, which is the starting- 

 point of a brood-body, evolves its constructive energy without receiving any special 

 stimulus from the protoplasm of a second cell of distinct origin, whereas for the 

 development of a fruit the necessity of such a stimulus is a charactei-istic and 

 distinctive feature of the phenomenon. Brood-bodies may spring from any part 

 of a plant. If the parent-stock as an individual is in danger of perishing, brood- 

 bodies are developed from protoplasts which otherwise would never have been 

 called upon to play such a part. Brood-bodies may develop on roots, stems, and 

 leaves, on foliaceous prothallia, and on hyphal filaments. They may be formed 

 above or below the ground, and upon or beneath the surface of water. Their origin 

 may be from superficial cells or from cells deeply seated in a tissue. It is scarcely 

 going too far to say that in cell-aggregates of large dimensions the protoplasm 

 of every young cell is potentially the starting-point of a brood-body. 



If a fruit is to arise, the ooplasm, i.e. the protoplasm destined to initiate a new 

 generation, must unite with the fertilizing protoplasm, which is called spermato- 

 plasm. The two protoplasts concerned in this phenomenon originate at separate 

 spots, and if they are to coalesce the space between them must be surmounted. 

 One at least of the two protoplasts must accomplish a change of place, and this 

 locomotion must take place in a definite direction. The union of two protoplasts 

 which have been formed at places separated in space from one another constitutes 

 the essence of the process of fertilization, and it results in a change in the ooplasm 

 which, in accordance with our idea of the minute structure of the substances in 

 question, may be looked upon as a displacement of molecules and an alteration 

 in their grouping. Sometimes this internal rearrangement is plainly manifested 

 externally by a change of form and colour, or by an increase in size; and where 

 this occurs it ensues immediately upon fertilization. But for the most part no 

 alteration in the fertilized ooplasm is perceptible at first, and it would be difficult 

 to specify any certain signs whereby the fertilized ooplasm may be distinguished 

 from the unfertilized. It is, however, known by experience that in most cases 



