.Tainiary, 1921. 



ftOTENTIFIC AGRICULTURE 



ill this collection of strains, the growth above 

 ground showed many striking variations with re- 

 spect to flower color, habit of growth, seeding 

 properties, and size and vigor of individual plants. 

 As the study of these plots i)roeeeded, it was 

 fiiinid necessary to go over the crop so as to root 

 u]) any superfluous plants which would interfere 

 with a study of individual plants. 



In carrying out this work, a practical acquain- 

 tance was obtained of the characteristics of the 

 Alfalfa jilants below the ground line. 



In the course of our observations, it was noticed 



that the crowns of different plants ))resented 



great variations; some were broad and sj)reading. 



producing man}' stems and buds, and usually 



having a branching root system. The ma.iority of 



the i)lants, however, had small crowns with a less 



tendency to spread, and produced jiropoi'tioiuitely 



a small number of stems; tliese phmts usually 



had either a single taproot, or one oidy slightly 



branched. 



These preliminary observation.s were used as a 



basis for further invej5tigations ; and, in order to 



present an account of the diversified forms of roots 



c.Kamined, an attempt will be made to arrange the 



different root systems into three main types under 



the headings A. B, C. 



Type A. — True root .system without underground 

 stems (2 forms). 



1. Single tap-root. 



2. Brandhed tap-root. 



Type B. — Branched tajj-root together with the de- 

 velopment of well-defined underground stems. 



Type C. — Branched top-roohsi with buds and aerial 

 roots as distinguished from the underground stems 

 in Type R. 



Description of the Three Types and Subtypes. 



Type A. — The true root systems of the various 

 plants varied very markedly, and two well-defined 

 forms were examined. 



1. The single tap-rooted form wa.s by far the most 

 common : this consists of one main tap-root from 

 whieli arise numerous small lateral roots. 



2. The branching tap-root. In this form instead of 

 there being only one main root, t,he tap-root develops 

 into several large roots. The branching usually 



Figure 1. — Root System — Type A. 1. Single tap-root 

 2. Brandling tap-root. 



1' igure 2. — Brandling Roots of a Special Plant. Selected for 

 hardiness and seeding properties. Tliis is a third gen- 

 eration plant from Sand lucerne. 



commences either immediately below, or a short dis- 

 tance below, the base of the crown, and the various 

 branches at first u.snally grow out in a lateral direc- 

 tion, but later take a more vertical downward cour.se 

 into tihe soil. 



Comparisons were made between the stems and 

 foliage of the plants having the different root sys- 

 tems, and the superioritv of t.bose having branalied 

 roots as compared with the single tap-root was very 

 striking, being usually much more vigorous and 

 liealthy in growth, and consequently yielding a mnclh 

 heavier crop. 



This examinntion. fliougli it was reararded as being 

 only of a preliminai-\- natui-e yet was sufficient to 

 furnish convincing evidence that in any attempt to 

 improve the strain.s of Alfalfa, the character of the 

 •■oot system should be considered to be of primarA- 

 importance. 



One of the greatest advantages to a plant having 

 a branched root sy.stem over the single tap-root is 

 the mudh firmer anchorage it gives to the plant ; 

 thus enabling it to resist far more effectuallv anv 

 tendency to be heaved out of the .soil by winter 

 frosts and .spring thaws. " • 



It is a fact well-known to Alfalfa growers that one 

 of the most common causes of failure to retain a 

 p"ood stand is not so T'lueh flie low temperatures ex- 

 nevieneed durinsr winter as t.he alternate freezing 

 ^ind thawing which mav oi'"ur in tlie snrin". The 

 .Alfalfa is heaved out and the roots exposed i" such 

 a wav that a comnarativelv 'iffht fi-ost is sufficient 

 to destrov th" maioritv of the plants. It is under 

 such eondi1ie.i« that t.he plants witli the branched 

 rpn+s are seen to great advantage. 



This was clearlv demonstrated in the stiring of 

 Iflli The previous wii't"r. theu'rh no verv low tem- 

 neratu'-e; were recorded, proved to be very severe 

 on Alfalfa b^th on the nevvlv sown field.s and also 

 o'l those well-established, many good stands being 

 killed out. 



The chief i-ea.son for tiliis was t.iie unusual amount 

 of alternate freezing and thawing during the winter 

 !)"d sprimr vyhich heaved out the plants, thus expos- 

 iuf the roots to spring frcsts and drying winds. 



On the experiment i)lots seeded down in 1012. it 

 was found that those plants having a single tap- 



