202 Metrical Attributes of Wheat Plants 



simply to tin- "eiul-iJiotluct " (tlit- inature plant) but to the more iiu- 

 portant life-stages by whicli tlie end-product is determined. 



<j \\. The Inter-r?:i,ationship.s of the Tillers of a Plant 



IN REGARD TO CERTAIN MEASURABLE CHARACTERS. 



Glume-length, rachis-length, and the ratio of these two, were deter- 

 mined for every ear of every plant of Polish and Kubanka (1920 erop). 

 Ear-to-ear correlations (same plant) are given in Table III. It is plain 

 that first and second ears are more closely correlated than first and 

 third; further, correlations for rachis-length are slightly higher than 

 those for glume-length. Of the actual coefficients of correlation it may 

 be said that they are statistically significant but are not very high (their 

 general value is about | ()-."3). 



Table III. Ear-to-ear Correlations on the Indiridunl Plant. 



Value o( r for 



Variety and ^ — '• ■ -., Ears per 



no. of plants /■ for fJluraelength Rachis-length Ratio plant 



Polish (110) ICiirs 1 .-xnd L> OvWl j.0().">0 0-66.5:;; 0036 0-5l2±0-047 2 



I'olish (38) Ears 1 and :! (1-42!) j;()0S9 0-439±0-080 0-428±0-089 3 



Kubanka (107) Ears 1 and 2 0-,Wni0042 0-li.">!ti0037 0-699±0-033 2 



The first inference from these iigures seems to be that, when dealing 

 with the glume or with any similar ear-character, it is essential to confine 

 the observations to one ear per plant. In that, as a very general rule, 

 the ear of the main stalk is formed first and attains the greatest growth, 

 it is the best ear of the plant for observation. This inference from the 

 facts of inter-tiller correlation naturally leads one to ask whether, in 

 furtherance, it would be well to limit the experimental population to 

 plants which all possess the same total number of tillers or which all 

 ripen the same number of ears. Upon this point further evidence is 

 available and it is set forth in Table IV. The facts are quite clear and 



Table IV. Mean Values for the main tillers of plants grouped 

 according to the number of ears -per plant. 



Mean value (main tillers only) of 



• " ^ -^ 



Olnme-length Rachis-length Ratio 



26-.->!017 !)2-I±0-90 0-298±0-002 



30-0±017 118-4±l-0.i 0-262±0-002 



I0-9±00.5 58-0±0-50 0-196i;0-002 



ll-7-i;000 68-5 + 0-7.5 0-17o±0-001 



rather striking. Although only the main tiller was observed in the case 

 of every plant, the one-ear and two-ear plants give very different results. 



