Dec, 1921] PATON — POLLEN AND POLLEN ENZYMES 483 



thought served as the food of the pollinating insects. Tischler (1910, pp. 

 219-242) has studied this subject and has made the interesting discovery 

 that in certain pollens, at least, the sterile grains may be stimulated to 

 produce tubes by the addition to the culture medium of a trace of saliva 

 or of diastase. The lack of a specific enzyme in these pollens seems thus 

 to be the cause of sterility. It is quite possible that in other pollens the 

 lack of pectinase, cytase, invertase, or of other enzymes may be equally 

 important in inhibiting the growth of the tube. In some cases the deficiency 

 may be made good by an enzyme secreted by the stigma. The whole 

 question has a great deal of significance in problems of plant breeding. 



Pollen enzymes may be concerned in the production of the characteristic 

 odors of pollen which are probably factors in insect attraction. The ema- 

 nations from moist pollen indicate the presence of fermentation products. 



It also seems reasonable to suppose, as Erlenmeyer (1874, p. 206) has 

 suggested, that pollen enzymes are co-workers with the enzymes from the 

 body of the bee used in producing bee-bread. 



Gardeners commonly believe that contact with pollen is frequently the 

 cause of the discoloration and decomposition of the petals which is often a 

 sequence of pollination. 



II. Experiments in Regard to Pollen Enzymes 

 Plan of the Experiments 



An effort has been made to collect a large variety of pollens, representing 

 different families of plants, and including some of the so-called "hay-fever 

 pollens." These pollens have been tested for twelve different enzymes. 

 On account of the difficulties in collecting all the pollens at the start, the 

 experiments have been made in two series. For the first the available 

 pollens were those of (1) Easter lily, (2) Lilium rubrwn, (3) red maple, (4) 

 Norway maple, (5) Siberian crab-apple, (6) Austrian pine, (7) Scotch pine, 

 (8) magnolia, and (9) dandelion. In the second series of experiments, in 

 addition to some of the first nine pollens, those of the following plants were 

 used: (10) corn, (11) daisy, (12) dock, (13) elm, (14) goldenrod, (15) rag- 

 weed, (16) rye, (17) tiger lily, (18) timothy. Not every one of the eighteen 

 pollens has been used in every test, but an effort has been made to use as 

 many as possible. 



Methods of Collecting Pollen. Kinds of Pollen Used 

 The work was begun in February. At this time Easter lily pollen was 

 available in the largest quantity. Since it is customary to remove the 

 anthers as the flower opens, to prevent the pollen from staining the petals, 

 it was easy to find an obliging florist who would place these anthers in a 

 clean paper box. In this way surprisingly large quantities of pollen were 

 secured. Care had to be taken to prevent molding. A paper box was 



