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 Wiesner'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 



