April I, 1920 



A Teosinte- Maize Hybrid 



25 



NODES SILKING GROUP 



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NODES SII.KING ON THIRD 



This character, which is the number of nodes producing silk on the 

 third branch from the top, was chosen with the idea of indicating the dis- 

 tinction between teosinte and maize with respect 

 to the production of secondary fruiting branches 

 on. the upper part of the main culm. In all va- 

 rieties of maize, branches from the upper part of 

 the plant are normally simple, though secondary 

 ears are a common abnormality. The branches 

 of the ears of Zea ramosa are not subtended by 

 bracts, and they arise from separate internodes 

 only in the sense that branches from the tassel 

 represent separate internodes. 



Teosinte normally produces silks at two or 

 three nodes of the third branch from the top. 

 The average for 87 Florida teosinte plants was 

 2.3, with a range from o to 4. Since there are 

 seldom more than 4 nodes on the third branch, 

 the difference is more significant than the num- 

 bers would make it appear. 



In the F2 hybrid plants the range was from o 

 to 10, with the mean at 5.5. 

 The distribution (fig. 21) is 

 practically symmetrical and 

 unimodal. 



There are three significant 

 correlations with this char- 

 acter, but all appear to be 



physiological. The positive correlation with nodes 

 on third branch is obviously almost physical ; that 

 with male secondaries is only slightly less so. 

 The correlation with position of best spike of 

 0.47 might be considered a disherence, but it 

 seems not unreasonable that with more nodes 

 silking the best spike would, on the average, be 

 located farther from the base. This is supported 

 by the negative correlation of node silking index 

 with position of best spike. 



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Fig. 20. — Alicole index: fre- 

 quency distribution of 

 plants in Fj. Class val- 

 ue, 10 percent. 



Fig. 21. — Nodes silking on 

 third: frequency distri- 

 bution of plants In F2. 

 Class value, one node. 



NODES SILKING INDEX 



The number of secondary branches silking as expressed in the pre- 

 ceding character is very definitely associated with the length of the third 

 branch, the branches with more nodes having the greatest number 



