Dec, 192 1 ] PATON POLLEN AND POLLEN ENZYMES 483 
thought served as the food of the poUinating 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. 
Poller 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 famihes 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 (i) Easter lily, (2) Lilium rubrum, (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, (ii) daisy, (12) dock, (13) elm, (14) goldenrod, (15) rag- 
weed, (16) rye, (17) tiger Hly, (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 
