Beer. Development of tlie pollen grain and anther of some Onagraceae. 299 
I might occupy many pages in quoting similar measure- 
ments but as tbose which I have already mentioned are qnite 
typical of tlie rest it would serve no nseful purpose to do so. 
The general result has been to show that in 0,6% Na CI. 0/75 % 
Na CI, 6% cane-sugar, egg-white and the plants own jnice the 
protoplast has a very similar appearance and its measurements 
agree very well witli one another at the different stages. 
Moreover, after remaining in these Solutions for some time 
little or no alteration, either in size or appearance, was obser- 
vable. The average measurement in 
from all my notes are as follows; 
these Solutions calculated 
Pollen grain 
pollen cavity 
pollen protoplast 
10 fi 
26 fi 
26 fi 
62 ^ 
37 fi 
27 fi 
70 ^ 
39 u 
32 fi 
74 y 
42 fi 
34.25 fi 
80 fi 
• 46 fi 
34 . o ji/. 
Strong Meinmings solution and strong chrom-acetic solution 
do not alter the protoplast very much in appearance but usually 
cause some shrinkage. 
Merkels fluid was not so satisfactory and it causes the 
kJ 
vacuoles to swell up and the protoplast to enlarge. 
Absolute alcohol causes very considerable contraction of the 
protoplast. 
Distilled water enlarges the vacuoles and causes thera to run 
together by breaking down the separating arms and laminae 
of cytoplasm. Consequently the whole protoplast swells up 
great ly. 
Objection may still be taken to conclusions drawn from a 
study of the living pollen in the plants own juice, the salt Solu¬ 
tions and in egg-white, on account of the possible infLuence 
which the mechanical Operation of teasing out the pollen grains 
may have exerted. 
That mechanical disturbances can affect the living contents 
of these cells is shown by the fact that if tlie pollen grains, in 
e. g. 0,6 % Na CI solution, are covered by a cover glass and the 
pressure due to this is not relieved the protoplast gradually en¬ 
larges and may finally hll the cell-cavity. If, however, the pre- 
caution be taken, of preventing the pressure of the cover glass, 
by a fragment of anther or filter paper or by not covering the 
preparation at all no such change takes place in the protoplast. 
An error from this cause, however, is extremely improbable 
as the pollen grains can be drawn out from the anther without 
actually subjecting them to the touch of an instrument and with 
only very little pressure or friction. This can be done by means 
of the fibrous mucilage which surrounds the pollen grains and 
binds them together in long strings. 
Moreover microtome sections of pollen grains, fixed whilst 
lying untouclied within the anther, show a rough parallel in 
