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STUDIES ON POLLEN, III. 
F. M. AnprEws, Indiana University. 
Since the appearance of my second contribution on the study of pollen I 
have continued my investigation on this subject and have added a consider- 
able number of plants to those already studied in ways mentioned in my 
previous papers. As the work has progressed certain new methods have 
suggested themselves as expedient or in many cases as necessary for the 
proper advance of the work. One former method of allowing pollen to be 
placed for germination in the desired solution between a slide and cover- 
glass is, while often giving results, unfair since certain life processes can 
not normally be carried out under these conditions. The use of an ordinary 
glass ring cell cemented to a slide and having the pollen for investigation 
in a hanging drop also served in many cases but allowed of no regulation of 
temperature by an exchange of air in the ways desired. A common gas 
chamber served the purpose better and obviated the difficulty just men- 
tioned and also allowed of certain other forms of experimentation, not 
possible with the glass ring cell, that I hope to investigate later on. In 
this last type of culture cell, as here used, it was necessary to use wet 
filter paper in the cell or a small quantity of water to prevent the specimen 
from drying up. All the culture cells mentioned thus far had the disad- 
vantage of allowing only one experiment or culture to be so arranged at 
one time. To offset this the glass ring sell was used in large numbers but 
individual cultures made in this fashion require a great deal of extra work 
and are not conducive either to convenience or accuracy. In some cases at 
first when an extra large number of cultures were to be made I suppli- 
mented the glass culture ring apparatus by cells made of filter paper and 
kept moist in damp air under a bell jar. These latter, however, were much 
less satisfactory for various evident reasons. 
Since my second contribution on this subject I have increased the number 
of plants whose pollen I have studied from 435 to 540. In the case of all 
of these 540 plants I have tried to grow the pollen in the following solutions : 
distilled water and cane sugar of 1%, 5%, 10%, 15%, 20%, 30%, 40%, 
50% and 60%. A great many, of course, did not grow but many did. The 
pollen of all of these 540 plants were experimented with in this way and 
given a trial even though, as is well known, some few of them have not 
yielded results in this way. Of these 540 phanerogams only the pollen of 
five produced more than one tube on germination. This is very different 
from some pollen which produces many tubes on germination as in the case 
of Malva crispa. Of all the 540 plants I found only one whose pollen tube 
branched. That was the pollen of Caladium bicolor one of whose pollen 
tubes branched three times and two of whose pollen tubes branched twice. 
The record of this plant is as follows. viz: In distilled water ten pollen 
grains in one hundred germinated. In the cane sugar solutions 21 germin- 
ated in the 1%; 4 in 5%; 0 in 10%; 3 in 15%; 27 in 20%; 15 in 30%; 3 
in 40% ; 0 in 50%, and 0 in 60%. The pollen in this experiment was all 
of the same age and grown under exactly the same conditions. The first 
point of interest, therefore, is that in 10% none grew while just above and 
