19161 AGRICULTURAL BOTANY. 731 



vested in one year supplying the plants for the next season but one. Single 

 plants were found to be slower growing from the first and to present a less 

 robust appearance at the time of planting out than their sister doubles of the 

 same sowing. The results of the tests made entirely refute the statement that 

 this particular strain is in any way exceptional as regards the output of doubles. 

 It is thought that when the vegetative period is sufficiently prolonged to render 

 the method of selection by vigor practicable, this method may be successfully 

 employed by the gardener, securing in this way a much larger proportion of 

 doubles than is ordinarily obtained. 



A suggested explanation of the abnormally high records of doubles quoted 

 by growers of stocks (Matthiola), Edith R. Saunders (Jnnr. Genetics, 5 

 {1915), No. 2, pp. 137-U3). — The author states that she is now able to give in 

 full the evidence upon which rests the main conclusion in her paper noted 

 above. This evidence is said to be based upon a comparison of results ob- 

 tained in the flower bed with those of a controlled experiment employing the 

 same materials, showing that the apparent excess output of doubles in the first 

 case is fictitious, and upon a comparison of the number of singles and doubles 

 recorded among the more and the less vigorous individuals, respectively, show- 

 ing that a proportion in excess of expectation furnished by the more vigorous 

 individuals is counterbalanced by a corresponding deficit among the less vigor- 

 ous plants. The conclusion is reached that doubles on the whole develop more 

 rapidly and vigorously than singles, and that when the period of development 

 is sufficiently prolonged, selection based upon this difference can be used as a 

 means of securing a higher number of doubles in the beds than corresponds 

 with the actual number from the parent plants. 



On the relation of half-hoariness in Matthiola to glabrousness and full 

 hoariness, Edith R. Saunders (Jour. Oenetics, 5 {1916), No. S, pp. 145-158). — 

 An account is given of further studies of the relation between hoariness or 

 glabrousness and sap color. These studies are said to establish fully the 

 conclusions formulated in a previous report (E. S. R., 28, p. 228). 



The results recorded in this and the earlier paper are considered to form a 

 concordant body of facts concerning surface character which the suggested 

 scheme of factor relations allows to be brought together in a comprehensible 

 whole. These factor relations are supposed to involve five factors, which inter- 

 act as three distinct pairs. The behavior of the different paired factors Is 

 described at length. 



Pollen sterility in relation to crossing, R. R. Gates and T. H. Goodspeed 

 {Science, n. ser., 43 {1916), No. 1120, pp. 859-861). — Preliminary observations 

 made on a number of species of plants indicate that geographically isolated 

 species do not invariably have good pollen and that pollen sterility is by no 

 means a sure sign of hybridity. Pollen sterility is considered a physiological 

 condition which occurs in all degrees of intensity and may be due to a variety 

 of causes, hybridity being one of them. 



On the germination of the pollen grains of apple and other fruit trees, 

 J. Adams {Bot. Gaz., 61 (1916), No. 2, pp. 131-147).— Giving the results of pre- 

 liminary observations made in 1913 regarding the germination of pollen grains 

 in cane sugar solutions ranging in strength from 2..5 to 50 per cent, most of the 

 experiments relating to apple, the author states that some varieties of the same 

 species appeared to have more vigorous pollen grains than others. The pollen 

 grains germinated either in light or in darkness. The quickest germination 

 was observed at temperatures of 21 to 23° C. (69.8 to 73.4° F.). A few pollen 

 grains of apple formed short tubes after being kept dry for three months, some 

 of pear after ten weeks. Pollen grains of strawberry, loganberry, and rasp- 

 berry were dead after two months, those of black currants after eleven weeks. 



