24 PB ACTIO AL GUIDE TO GABDEN PLANTS 



THE SEED 



It has been stated above that the growth of a plant takes the form 

 of a cycle, and it is therefore difficult to take any one organ and say 

 ' growth begins here.' This cannot be said of the root, as it is the out- 

 come of the seed ; it cannot be said of the leaves, as they are outgrowths 

 of the stem ; and it cannot even be said of the seed, which is produced 

 by the ripened fruit. As, however, for practical purposes it is necessary 

 to start somewhere, the most logical beginning from a gardening point 

 of view seems to be the Seed, which we will therefore consider. 



Many years ago, the late Dr. Lindley described a seed as being ' a 

 living body, separating from its parent and capable of growing into a 

 new individual of the same species. It is a reproductive fragment, or 

 vital point, containing within itself all the elements of life, which, how- 

 ever, can only be called into action by special circumstances.' 



As popularly understood, seeds are only produced by Flowering 

 Plants or 'Phanerogams ' (p. 121). They are the result of the ovules 

 (either naked, as in the Pine order ; or enclosed in carpels, as in most 

 other Flowering Plants) being fertilised by the pollen tube. Each fer- 

 tilised seed contains an embryo, or the rudiments of a young plant. 

 When placed in a suitable temperature, with moisture, they are capable 

 of reproducing all the characters of their parents. The so-called 

 ' seeds ' or spores of Ferns differ very much from those of Flowering 

 Plants, and the way in which they are reproduced is explained at p. 1009. 



The process of forming seeds takes place somewhat in this way. 

 When the grain of dust or pollen from an anther in the flower falls 

 on to the stigmatic surface of the carpel, the grain of pollen begins to 

 grow much in the same way as a seed in the soil, with the exception 

 that all the growth is downwards. A microscopic thread called the 

 pollen tube makes its way from the pollen grain downwards through 

 the tissue of the carpel, and eventually reaches the ovule contained 

 within the walls of the ovary. At one end of the ovule there is a small 

 hole called the micropyle. The pollen tube enters this and comes in 

 contact with a cell much larger than the others called the embryo-sac. 

 Within the embryo-sac and close to the micropyle are three other cells, 

 one of which called the egg-cell or embryonic vesicle receives the contents 

 of the pollen tube and is thus fertilised. This operation, sooner or 

 later, results in the production of what is commonly known as a seed. 

 After fertilisation, the nuclei in the masses of protoplasm in the cells 

 divide as explained above and form new masses, and thus fill up the 

 interior of the embryo-sac. Eventually the embryo, or young plant, 



