426 SECTIONAL TRANSACTIONS.— K. 



capable of germination later when conditions are suitable. The problem 

 is complicated by the fact that in the case of most weed seeds little is known 

 of the length of the resting period of normally ripened seeds. For this 

 reason it has been necessary to study the resting periods of the seeds of the 

 various weed species together with the first problem. 



Semi-popular Lecture by Dr. M. A. H. Tincker on Growth-promoting 

 substances and horticulture (5.0). 



Investigations by Went, Kogl, and others led to the isolation and chemical 

 recognition of the plant hormones, auxin a and b. Hetero-auxin, P-indolyl 

 acetic acid, associated in certain animal products with the former sub- 

 stances was also observed to influence the growth of plants. This more 

 readily available, simpler chemical may be applied to plants as a paste using 

 lanolin, or in solution in water. Many compounds have been tested by 

 Zimmerman and others ; a-naphthalene acetic acid is highly active at great 

 dilution. 



P-indolyl acetic and a-naphthalene acetic acid induce the formation 

 of roots. 



For vegetative propagation they are now used in practical horticulture 

 to facilitate and accelerate the development of roots from cuttings, herba- 

 ceous and woody. Roots are developed more rapidly in greater numbers 

 on each cutting, whilst the number of cuttings which form roots is con- 

 siderably increased by these growth substances. Many species and varieties 

 have been tested and showed these responses, which vary in quality according 

 to the season of treatment and the correlated nature of the material chosen. 



The chemicals are taken up conveniently by leafy cuttings, placed with 

 their basal ends in a solution for twenty-four hours. 



Roots may develop some small distance from the point of application of 

 the chemical. Inhibition of foliar development frequently results if cuttings 

 are taken before the buds have opened. Anatomical changes result from 

 the stimulation including rapid cell division in meristematic tissue, cambium, 

 in vacuolated parenchyma, and in differentiated tissue. 



Saturday, September 4. 



Excursion to Miller's Dale, Chee Dale and Froggatt Edge. 



Sunday, September 5. 



Excursion to Sherwood Forest and Newstead Abbey. 



Monday, September 6. 



Discussion on Genetics and taxonomy (lo.o). 



Dr. W. B. Turrill. — The expansion of taxonomy. 



(i) Introduction. — The necessity and practical aims of classification. 



(2) Alpha taxonomy. — Its methods, achievements, continuation, and 

 limitations. 



(3) Omega taxonomy. — The new ideas and ideals. The introduction of 

 experimental methods. The reactions between taxonomy and 



