Page:Report of the Puerto Rico Experiment Station (IA CAT31294391015).pdf/18

 and red bean, are superior to less vigorous perennials or to annual legumes, such as cowpea and Florida velvetbean. In the rubber field, the application of ammonium sulfate to grass plots seems to be more practical, to date, than the use of grass-legume combinations in increasing forage yields.

Test plots of 131 introduced and native legumes have been established. The purpose of these plots is to study some of the legume characteristics, including (1) type of growth, (2) whether annual or perennial, (3) flowering season, (4) seeding, (5) disease and insect incidence, and (6) adaptation to climate. Most of the species have already flowered and seeded. Among those showing promise under the plot conditions are Crotalaria paulina, C. usaramoensis, Canavalia ensiformis, C. bonariensis, and certain varieties of Dolichos lablab and Cajanus indicus. A group of 6 alfalfa strains made good early growth but subsequently have not developed well. Three species of Lespedeza and the 10 strains of Lupinus, as well as one species each of Vicia, Onobrychis, and Trifolium did not survive the conditions in the south field.

R. H. Freyre, R. Fernández Pol, and H. E. Warmke

Preliminary results of chemical analyses of Merker grass from grass-legume plots show that the percentage of nitrogen and total yield of crude protein are increased when Merker grass is grown in combination with legumes, as compared with Merker grass grown alone. These analyses also indicate that grass grown in combination with legumes may be richer in the important minerals, calcium, magnesium, potassium, and phosphorus.

R. H. Freyre and H. E. Warmke

Interspecific hybrids from crosses between Stizolobium deeringianum Bort. (Florida velvetbean), S. aterrimum Piper and Tracy (Bengal bean), and S. pruritum (Wight) Piper and Tracy (pica pica) were studied as to the mode of inheritance of certain genetic characters. These studies indicate that the hairiness on leaves and stems and the obnoxious stinging hairs of the pica pica pods are largely dominant over their alleles in the other two species, with the degree of hairiness varying somewhat in different crosses. Hairy pods with glabrous leaves and stems were obtained in one case when two hairless velvetbean varieties were intercrossed, thus suggesting that hairiness on pods and on leaves and stems are independent characters and that pod hairiness may be the result of complementary action. The black color of the Bengal bean seed is dominant over the mottled condition in the other species. An intermediate amount of speckling was obtained when two varieties varying in degree of speckling were crossed. Shape and size of seed are also probably determined by genetic factors, seeds in the F, having the tendency to be intermediate between parents.

Entire plants of tropical kudzu, when covered with cages of copper screen, set very few seed pods, while unprotected control plants set abundant pods. Since the keel in kudzu flowers appears to open only rarely so as to expose the stigma before the blossom falls, this species was assumed to be largely self-pollinated. The high degree of sterility under the cages, therefore, was unexpected. Experiments are planned to determine whether the failure of seed setting under the