8 



BULLETIN" 289, U. S. DEPARTMENT OF AGEICULTUEE. 



(fig. 2, B). The stigmatio surface is papillate and has a fringed 

 appearance in the mature flower. The papillse contain much oil and 

 have rather heavy walls, which react to the test for cutin. 



Both ovules develop embryo sacs (fig. 2, 0). Fertilization usually 

 takes place in each ovule; but only one, so far as observed, matures 

 into a seed. Should plants occur that mature both ovules, there 

 would be an opportunity to produce strains with twice the seed- 

 yielding capacity of those now grown. 



^-a 



Fig. 2. — Red-clover flowers, showing different stages of development. A. — Lengihwi ;e section of a red- 

 clover flower at an early stage (X50): a, Calyx tube; 6, staminal tube; c, standard; d, one of the long 

 stamens; e, anthers of two long stamens; /, free stamen; g, stigma; h, the two ovules; •/, anther of a short 

 stamen; j, stylar canal. B. — Lengthwise section of an open flower, showing the character of the stigma 

 and its position relative to the anthers (X25): a, Stigma; 6, anthers of two long stamens; c, anlhers of 

 two short stamens. C. — Lengthwise section through the base of a flower, open and ready for fertilization 

 (X40): a, Egg; 6, endosperm cell; c, calyx; d, staminal tube; e, nectar glands;/, free stamen. D. — A 

 median, longitudinal section through the nucellus of a sterile ovule which should have been ready for 

 fertilization, the flower being open; all cells remained vegetal ive and no reproductive cells were produced 

 (XlS). E.— Pollen grain (X325): g, Germ pore; n, nucleus; ir, wall. 



INFERTILE OVULES OP RED CLOVER. 



Infertile ovules are a common occurrence in red clover and occur to 

 a considerable extent throughout the season. A section ( I trough the 

 nucellus of an infertile ovule is shown in figure 2, IK In the infertile 

 ovules nil eells remain vegetative and no embryo sac is formed. The 

 largest percentage of infertility hits been found to occur in first-crop 

 red clover, ;in<l litis infertility appears to accompany moist soil and 

 atmospheric conditions. During I he first crop many plants produce 



