198 GENETICS [Bot. Absts., Vol. V, 



number of rows on the ear, per cent of grain to cob, weight of 100 seeds, and time of maturity. 

 — It was found that in selecting for yield of grain the best results were obtained when the prog- 

 eny row was taken as the unit of selection rather than the individual plant, although positive 

 results w-ere obtained in either case. — Selection for number of rows was ineffective since the 

 progenies regressed to a f ourteen-rowed type regardless of whether the selection was made for 

 a greater or less number of rows. — The per cent of grain to cob was found to be readily changed 

 by selection but it was found also that the size of the cob was directly associated with the 

 yield of grain. Care, therefore, must be exercised in selecting for an increased ratio of grain 

 to cob, not to reduce the absolute size of the cob. — The author questions the value of many- 

 eared strains and restricted selection to single-eared plants. — J. H. Kempton. 



1503. Florin, Rudolf. Zur Kenntnis der Fertilitat und partiellen Sterilitat des Pollens 

 bei Apfel- und Birnensorten. [On the fertility and partial sterility of the pollen of different 

 varieties of apple and pear.] Acta Horti Bergiani 7: 1-39. 1920. — If there is self -sterility or 

 insufficient power of germination of the pollen of a variety of fruit trees it is not advisable to 

 grow the variety in question alone in great closed groups, but other sorts should be grown 

 among them which produce plenty of pollen with great efficiency. Author has examined the 

 power of germination of the pollen (in solutions of sugar of variable concentration) of 102 

 apple and 14 pear varieties, which are cultivated in Sweden. He gives a tabulated summary 

 of 405 experiments, wherein he states date, time of examination, temperature, per cent of 

 germination and maximum and minimum length of the measured pollen tubes. — Of the apples 

 24 sorts showed 0-30 per cent of germination; 13 showed 31-70 per cent; and 65 showed 71-100 

 per cent. The last group is of course the most preferable for use as pollenizers. A list of 

 literature is given containing 27 citations. — K. V. 0$sia?i Dahlgren. 



1504. Foot, Katharine. Determination of the sex of the offspring fiom a single pair of 

 Pediculus vestimenti. Biol. Bull. 37: 385-387. Dec, 1919. — A pair of fleas produced 143 fer- 

 tilized eggs. Of these 125 hatched and the sex was determined for 115 of the young or 92 per 

 cent of the total. There were 62 males and 53 females. The earlier-produced eggs yielded 

 a higher percentage of females than males. Later the proportion of the sexes became equal 

 and then, as the last eggs were produced, the earlier sex ratio was reversed — more eggs 

 developing into males than females. — D. D. Whitney. 



1405. Fraser, Allan Cameron. The inheritance of the weak awn in certain Avena crosses 

 and its relation to other characters of the oat grain. Cornell Univ. Agric. Exp. Sta. Mem. 

 23 : 635-676. June, 1919. — A study is made of the inheritance of the weak awn in Avena crosses. 

 Burt oats were used as parent for the weak awn and Sixty Day for awnless. The reciprocal 

 crosses indicated an approach to dominance of awnlessness. In F 2 generations, two distinct 

 classes of the weak awn and awnless appeared with a variation between the two types of about 

 all the possible differences between the parent sorts. These intermediate forms could not be 

 separated into classes on a multiple factor basis. If all these intermediate forms were thrown 

 into one class, there would be a close approximation to the 1:2:1 ratio. The fully awned type 

 is evidently pure recessive. Data in F 2 or F 3 generations did not include the entire plant, 

 the center spikelet only being used. This method was based upon results of Love and MoRos- 

 tie on the tendencies of the plant to agree in its characteristics with the terminal spikelet. 

 The data seemed to show that both parents contain a factor for awning, but that the Sixty 

 Day parent possesses an inhibitor linked with yellow color. The inhibitor seems to be 

 affected in its power of inhibition by environmental factors. The partly awned plants in F 2 

 generations are shown to be heterozygous in successive progeny types. Spikelets with two 

 awns on a kernel are found only on completely awned spikelets. Increase in soil moisture and 

 nitrogen seems to decrease number of awns. — The appearance of strong and intermediate 

 awns in F 2 and F. ? progenies is considered to be a reversion. There is strong linkage shown 

 between medium long basal hairs and the awned condition. Short basal hairs or no hairs are 

 dominant over long basal hairs. — With respect to color, the Fi plants are intermediate. On 

 account of the difficulty of determining color under weather conditions, the F 2 is not consid- 



