MUTATIONS, VARIATIONS, AND RELATIONSHIPS OF THE OENOTHERAS. 15 



pollen to other causes than the ingrowth of the tapetum to fill the loculus. 

 He found that development may proceed to the formation of tetrads, but 

 frequently degeneration begins in the resting stage of the first mitosis. The 

 successful pDllinations recorded below, however, demonstrate the functional 

 maturity of the pollen in many cases. Heterochromosomes were found to 

 arise in the prophase after synapsis, both in lata and in the lamarckiana hybrid 

 with lata. Inferential support was secured for the supposition that the 

 changes constituting mutation occur during the reduction divisions. 



The pistil is barely longer than the stamens, with the stigmatic lobes, heavy 

 and club-shaped, 6 to 7 mm. long. The capsules are 13 mm. long, about 6 to 7 

 mm. in diameter in the thickest portion, finely pubescent, many angled, and 

 tapering slightly toward the apex. The terminal rosettes on the stem and 

 branches were small and regular. 



While this form has hitherto been found incapable of producing mature 

 pollen capable of effecting fertilization in repeated trials made in Amsterdam 

 and New York, a notable exception is to be recorded. A package of seeds of 

 O. lamarckiana, which is growing wild near Birkenhead, England, was received 

 from Mr. C. Theodore Green in 1905. A sowing made from this lot yielded the 

 parental form, rubrinervis, and a few individuals of lata, which agreed with 

 this form as derived directly from pure cultures so far as all external charac- 

 ters were concerned. Many individuals previously examined in various 

 laboratories showed pollen which appeared normal under the microscope, yet 

 no fertilizations could be secured. In the present instance, however, pollen 

 appeared so plentiful that another attempt was made, the treated pistils 

 being carefully guarded from pollination from the parental or other forms. 

 A few pods were matured and some seeds were secured as a result. These 

 were sown as soon as ripe, in September, 1906. The progeny showed 10 lata, 

 So lamarckiana, i albida, and 3 oblonga. No material difference between this 

 and progenies resulting from pollination with lamarckiana was thus shown. 

 In the latter case the proportion of lata is often as low as 4 per cent of the 

 entire progeny and has not been recorded to have gone beyond 45 per cent. 



.OENOTHERA OBLONGA. 



O. oblonga was first observed by De Vries at Amsterdam in 1895, although 

 it doubtless appeared in his cultures previous to that time, as he suggests. In 

 all it has arrived in 700 mutants and in the pedigree-cultures described in this 

 paper in 35 individuals, only a part of which came into bloom in August, 1905, 

 agreeing with the observations in Amsterdam. Oblonga is one of the most 

 easily recognizable of the derivatives of 0. lamarckiana, although the distin- 

 guishing characters do not readily lend themselves to taxonomic description. 



The rosettes are not very dense ; the leaves in the young rosettes are nar- 

 rowly ovate-lanceolate, rather thick and fleshy, with broad midveins which 



