INHERITANCE IN PLANT HAIRS 



Stinging Bristles of Wild Plant Black Tomentum of Velvet Bean — Fine Down of 

 Lyon and China Beans Coarse Down of Yokohama Bean — Stinging Bristles 

 of Hybrids — Nine-Sixteenths of the Second Generation Stinging — Three- 

 Sixteenths of the Second Generation with Black Tomentum on Plants 

 and Pods Fine, Coarse, and Intermediate Downy Pods — "Velvet" 

 Plants — The Third Generation — Working Hypothesis. 



John Belling, 

 Florida Agricultural Experiment Station, Gainesville, Florida 



MUCH useful information has 

 been gained by experiments 

 on the inheritance of the 

 color, length, and texture of 

 hair, fur, or wool, in animals. Oppor- 

 tunities for similar experiments with 

 plants have been rare. But in the 

 second generation of crosses between 

 the Florida Velvet bean and another 

 species of Stizolobimn', the Lyon bean, 

 seven distinct forms of bristles, tomen- 

 tum, and down cover the pods or other 

 parts of the different plants; while the 

 color of these plant-hairs varies between 

 red, yellow, gray, white, brown, and 

 black. Since each plant requires 64 

 square feet, there is no inducement to 

 grow families solely for the study of the 

 inheritance of the different kinds of 

 I^ubescence. However, in raising im- 

 proved constant races from the offspring 

 of these crosses, considerable attention 

 had to be given to the inheritance of 

 the covering of the pods, and some of 

 the main genetic differences have been 

 disclosed. As several members of the 

 American Genetic Association are in- 

 vestigating these ])lants, the following 

 short account of my results may ixThajxs 

 lead others to fill xxp gaps in our knowl- 

 edge which I have been unal^le to fill 

 as yet, although during each of the i)ast 

 four years the length of the rows of 

 pedigreed plants I have grown amounted 

 to about two miles. 



WILD STINGING POOS 



A wild Stizolobium from India (S. 

 pruritum) has its pods covered with 



red and yellow erect bristles less than 

 two millimeters long. Part of a pod 

 is magnified in Fig. 7. The bristles 

 readily come loose. Each has its tip 

 filled with a gummy substance, clearly 

 visible in Fig. 7. The tip of the bristle 

 is photographed on the left of Fig. 14. 

 Minute projections like barbs may be 

 seen. These projections form small 

 colorless knobs over most of the bristle, 

 but are longer and pointed near the tip. 

 The two most conspicuous novelties 

 resulting from the crosses were stinging 

 bristles like those of this wild plant, 

 and smooth black pods. These are 

 shown, together with the pods of two 

 parents, in Fig. 8. 



THE PARENT PLANTS 



The Velvet bean (Fig. 8c) gets its 

 name from the nearly erect, black, 

 silky hairs of its young pods. Its ripe 

 pods are covered with a brownish-black 

 tomentum or wool (Fig. 9, left), the flat 

 twisted hairs of which are often over a 

 millimeter long. One of these hairs is 

 shown in the fifth place in Fig. 15. The 

 fresh tomentum from a nearly full- 

 grown pod is photographed in Fig. 11. 

 Some of the hairs are straight and color- 

 less, as are often the tips of the others. 

 They have minute knobs, and also a 

 little gum within the points. Men pick- 

 ing or threshing Velvet beans often 

 ex])eriencc irritation caused by the 

 tomentum. If a genetic factor to stiffen 

 and lengthen these weak hairs could be 

 added, they would become genuine 

 stinging bristles. 



'Those arc dcscrilx-d in Bui. 1 79 of the Bureau f)f Plant Industry, by C. V. Piper and S. M. Tracy. 

 348 



