1893.] THE MICEOSCOPE. 53 



EXAMINATION OF POLLEN TUBES. 

 By Henry Shimer, M. D. 



MOUNT CARROLL, ILL. 



The fertilization of plants is effected by pollen tubes which 

 reach down through the pistil to the ovary. The pollen is 

 carried by the wind or by gravity to the pistil and. adhering 

 thereto, sends down a shoot to the germinal vesicle of the ovule. 

 Unless this process takes place no seeds can mature and no plant 

 reproduce its kind normally. 



Having lost considerable time in studying the " shepherd's 

 purse " and the stramonium as recommended by certain books, 

 I at length obtained success with other plants, the knowledge of 

 which may be of interest. Professors Goodale and Strasburger 

 advise students to produce these growths artificially with sweet- 

 ened water, and give formulae for use with pollens of several 

 different plants named, but these are plants not readily at our 

 command. 



Gray in his "Structual Botany," p. 2S3. refers to a buckwheat 

 pistil. Several of these studies require sections to be made. 

 This is troublesome and few undertake it. 



I have had good views of pollen tubes in ray studies of apple 

 blossoms, and especially in the syringas, which gave me the 

 longest free tubes of all. By looking among the flowers, I often 

 found a few free pollen tubes ; but when T accidentally found them 

 in the pistils of the grasses already prepared for examination, and 

 in the greatest number that could be wished for, it gave me an in- 

 tense joy which I had never expected. 



These pollen tubes are little root-like sprouts, one or more 

 from each pollen grain. I think I usually see but one from a 

 single pollen grain of the grasses. These tubes may be seen in 

 situ on the stigmas of the cultivated grasses better than on the 

 stigmas of any other flower that I have examined. These grasses 

 have a very delicate, white, branching pistil. The stvle and its 

 branches are pale, white, and translucent. The style divides into 

 two branches near the little seed. There are many little branch- 

 lets on each one of these styles. They are like little limbs sur- 

 rounded by tooth-like tubes or cells. These cells correspond to 

 the papillae on the stigma of the higher developed flowers, as the 

 apple blossom. The stigma of the apple show r s these papillae 

 projecting from the crown of the stigma, the lower part of the 

 cell being imbedded in the body of the stigma. But in the 

 grasses these spur-like papillae stand around the branch in close 

 leaf-like order. They are short, projecting about 25 microns or 

 1-1000 of an inch long beyond the body of the branch, and about 



