The influence of seed age, planting depth, and temperature on the germination and emergence of ivyleaf morningglory [Ipomoea hederacea(L.) Jacq. var.hederacea], white morningglory(Ipomoea lacunosaL.), and entireleaf morningglory(Ipomoea hederaceavar.integriusculaGray) was studied by using pure seed of each taxa that were collected in 1972, 1973, and 1974. Germination of acid-scarified white and entireleaf morningglory seed ranged from 64 to 98% at continuous 20, 25, 30, 35, and 40 C and at an alternating 20/30 C cycle. The ivyleaf morningglory germination range was 50 to 98% at these temperatures, except at 40 C germination was <25%. Germination of nonscarified seed was generally 30 to 60% lower than scarified seed for the three taxa. Germination of seed collected in 1972 for all three taxa was less than 10% with 6 days of exposure to 45 C and 100% relative humidity, and germination of seed collected in 1973 and 1974 ceased with 12 days of exposure. Maximum emergence for all taxa occurred at planting depths of 1.3 and 2.5 cm. Seed age influenced seedling emergence of white morningglory and ivyleaf morningglory but not entireleaf morningglory. Total numbers of seed produced per plant for white, entireleaf, and ivyleaf morningglory were 15,200, 14,600, and 5,800, respectively.

Purple moonflower's (Ipomoea turbinata Lagasca y Segura) vegetative growth and seed maturation were characterized in noncompetitive field studies. Seedling emergence of 50% or greater of mature scarified seed occurred to a soil depth of 12 cm. At vegetative maturity a typical plant produced 11 primary, 50 secondary, 94 tertiary, and 7 quaternary runners having a total length of 185 m. The average number of leaves per plant was 1,120. Maximum seed size, seed wet weight, occurrence of first mottled seed, and first capacity to germinate occurred 20 days after anthesis in immature seed that were removed from the seed pod. Maximum germination occurred at 26 days after anthesis. Seed moisture content (dry weight basis) reached 8.5%, seed had formed an impermeable seed coat, and physiological maturity (defined as maximum dry weight) occurred 34 days after anthesis. The total number of purple moonflower seed produced per plant averaged 9350. The major mechanism of seed dormancy was impermeability of seed coats.

A perennial problem in cotton, Gossypium hirsutum L., involves obtaining a vigorous, uniform stand when planted early. Strains that grow roots longer and higher in relative root weight (mg/mm length) than currently used cultivars when temperatures are cool may help alleviate this. Using the standard cotton, cool temperature (18°C) germination test we determined root lengths and relative root weights for 124 day‐neutral composite F3 strains. Variability among lines was significant for each seed and seedling parameter. Fixed model diallel analyses of five strains indicated that among the five strains one would have difficulty in selecting for long roots with high relative root weight. Generation mean analysis indicated from one of two crosses that large amounts of additive, dominance, and additive by additive epistatic effects were present for the two primary root traits. One should thus be more successful if selection is delayed to the F3 to allow genetic recombination of additive and additive by additive epistatic genes to occur. Recurrent selection should be a useful method of breeding. The cross of strains 3822 ✕ 3851, involving accessions T‐214 and T‐225, respectively, should be useful for developing lines with root length equal or longer than ST 213 and relative root weight greater than ST 213. We speculate that plants with long roots and a high relative root weight should possess increased levels of resistance to seedling disease through a mechanical type of resistance; i.e., the plants should have more root tissue to slough off as diseased tissue and yet maintain a viable root system and a healthy plant than would plants with short roots with a low relative root weight.