Dec, 1921] 
PATON — POLLEN AND POLLEN ENZYMES 
477 
Agrostemma. Strasburger's illustration of the tubes actually penetrating 
and half filling the papillar cells of the stigma has been frequently copied. 
Mallow pollen tubes do the same. Recently Knight (1918, entry 964) has 
reported that in the apple there is no stylar canal. Pollen tubes make 
their way through the tissue. There is a decomposition of the cells along 
this path with the extrusion of mucilage." This is interesting to compare 
with the opinion of Grieg Smith that mucilages are decomposition products 
of cellulose, and with Wiesnei's statement that all gums are produced by a 
diastatic ferment acting on cellulose. The writer regrets that it has been 
impossible to secure corn cockle and mallow pollen so as to determine 
whether their enzyme action is different from that of other pollens. Apple 
pollen has shown some differences. In histological studies of fertilization 
little attention seems to have been paid to the question of how much the 
pollen tube disorganizes the neighboring cells. It seems that it would be 
worth while to examine material again with this thought in mind. Many 
of the drawings of the passage of the pollen tubes appear very diagrammatic. 
In this connection it is interesting to note Kerner's observation (1895, 
p. 392) that the pollen tubes of Lamium amplexicaule 
Perforate the walls of the anther and grow in the direction of the stigma until they 
reach it. 
Pollen Grains as Carriers of Bacteria and Molds 
Nine varieties of pollen were tested to see if any contained a rennin-like 
enzyme, such as is found in the juices of a number of plants. Thymol had 
been added to the unheated and autoclaved pollen extracts, but the milk 
had not been sterilized. It was observed that both the unheated ragweed 
pollen and the autoclaved dock pollen control had strongly coagulated the 
milk over night at room temperature. Repetition of the test with highest 
grade milk (Fairlea Farm) showed that unheated corn, Easter lily, and dock 
pollens caused clotting, as did even the autoclaved dock pollen. The strong 
''youghourt" or fermented milk odor, and the behavior of dock pollen 
made the reaction seem more like bacterial than like enzymatic action. 
Apparently the single period of heating in the autoclave had not destroyed 
all bacteria on dock pollen. Accordingly a number of tests were made 
employing the usual bacteriological methods. These tests showed that 
pollen grains harbor a varied flora of both bacteria and molds. It had 
been taken for granted that excess of toluol or of thymol was sufficient to 
inhibit bacteria and molds. Do the results of these tests with milk mean 
that in other instances it is the enzymes of bacteria and molds rather than 
those of pollen grains which cause the change? The writer believes that 
this is not true for the following reasons: 
a. The results were constant with the same pollen regardless of its 
source. Corn, pine, maple, and goldenrod pollen were collected both in 
New Haven, and, owing to the difference in seasons, a few weeks later on 
