The Science of Plant Growing 31 



Monocotyledons, like Lilies, Daffodils, Onions, Palms, and Grasses, the 

 primary root soon ceases to lengthen or dies, but its place is taken by 

 numerous, secondary, and even adventitious, fibrous roots. Some of these 

 attain a considerable thickness in large Palms and Screw Pines (Pan- 

 danus), but in grasses they remain slender and fibrous (fig. 16). 



Importance of Primary and Fibrous Roots. In 

 general terms roots serve to fix the plant in the soil. The 

 primary, descending root of forest trees is of considerable 

 importance to many of them, like the Oak, Elm, and Ash, 

 in preventing them from being overturned during gales 

 and hurricanes of wind. To gardeners it is of leading 

 importance in the case of such root crops as Carrots, Par- 

 snips, and Beet. Great care is taken in preparing the soil 

 to a considerable depth, and the seeds are sown where the 

 plants are to grow till they reach maturity. No trans- 

 planting is permissible. If the primary root or radicle were 

 broken, a shapely taproot would be impossible. All of 

 them could be transplanted with the greatest facility, 

 and, with care, almost every root would grow, but they Grafs -Fibrous d Root 

 would be short, stumpy, forked, misshapen, unsaleable, and 

 useless except for cattle. A deeply worked and well -pulverized soil is 

 necessary to enable the radicle to descend perpendicularly without twist- 

 ing or bending between stones and hard lumps; and if well manured for 

 some previous crop, the radicle and slender, lateral fibres will be well able 

 to forage for the requirements of a large and shapely root. It is quite 

 different in the case of Cabbages, Apple, Pear, and other fruit trees, 

 because transplanting multiplies the number of fibrous, feeding or absorb- 

 ing roots. The more fibres upon the roots of Cabbages, Onions, and the 

 like, the sooner they get established in their permanent positions when 

 transplanted. Taproots are undesirable in fruit trees, because they often 

 get down into uncongenial subsoils, while plenty of fibrous roots near the 

 surface induces early fruitfulness and permits of feeding. 



Relation of Soil to Roots. As already observed above, the root hairs 

 of plants apply themselves very closely to the particles of soil, in order to 

 absorb the thin film of water adhering to them. This film contains plant 

 food in a state of solution, and in greater quantity than in the root hairs 

 themselves, but at the same time the solution is very dilute and the root 

 hairs have to absorb a much greater quantity of water than is actually 

 required by the plant in order to get a sufficiency of food. The nature 

 of a soil bears a definite relation to its fertility. A sandy soil, being made 

 up of relatively large particles, can hold only a very limited quantity of 

 water, because the spaces between the particles are large and filled with 

 air. If manure is applied it rapidly decays and much of the plant food 

 in it is washed away into the drainage by rain. If liquid manure is 

 applied, most of it runs away. On the other hand, the particles of a clay 

 soil are much finer, hold more water and plant food, either in solid or 



