26 PB ACTIO AL GUIDE TO GARDEN PLANTS 



being done by the protoplasm in the cells as already explained. From 

 the water absorbed through the seed-coats, the protoplasm receives a 

 supply of food and proceeds to manufacture it, with the result that the 

 nuclei in the masfcs of protoplasm divide and produce other nuclei, and 

 these again in due course carry out the same process, not only until a 

 plant is fully developed but until it dies. 



Vitality of Seeds. — Some seeds retain their vitality for several 

 years — that is, their power of germinating does not appear to be much 

 injured by being kept a long time — while others very soon lose it. For 

 practical purposes it is preferable to obtain fresh and thoroughly 

 ripened seed to secure the best results. The stories as to the germi- 

 nating power of munmiy-wheat 2,000 years old are fables, but many 

 seeds will retain their vitality and produce good plants after careful 

 storing for 5 to 10 years. 



THE ROOT 



To the ordinary observer every part of a plant which happens to 

 grow naturally underground is regarded as a ' root.' This looseness of 

 expression is not altogether confined to the uninitiated, as the term 

 ' roots ' is also applied by florists and nurserymen to entire plants, such 

 as Pansies, Violas, Sweet Williams, Foxgloves, Double Daisies, and 

 many other plants in which a large trade is done during the spring 

 months. At present, however, we are chiefly concerned with real 

 roots, and it is necessary that the gardener should have a clear idea 

 as to their origin and function. 



The first Boot is the downward growth from the lower end of the 

 • caulicle ' or basal portion of the embryo. It usually breaks through 

 the seed coat at germinating time, before the cotyledons emerge to 

 the light, the object in view by nature evidently being that the young 

 plant should be provided with roots as early as possible after growth 

 has commenced in the seed. When the first root persists and continues 

 to grow it becomes what is known as a tap-root, and is present in all 

 Dicotyledonous plants (p. 131 to p. 805) raised from seed. Good examples 

 are seen in the Carrot, Parsnip, and Beetroot as represented at fig. 107 

 in the Glossary. As the tap-root in many plants has a tendency to 

 grow down into uncongenial and sterile parts of the soil, it may be 

 prevented from developing in a downward direction by more or less 

 frequent transplanting; this injures the tip, stops its growth, and 

 causes the more desirable fibrous roots to develop from the sides. 

 Eoots branch in all directions and apparently without system, and 

 become finer and more threadlike towards the tips. They usually 



