DEVELOPMENT OF THE POLLEN TUBE AND PROTHALLUS. 33 
structure (fig. 26), the meshes of the reticulum being rather large. 
The kinoplasmic filaments are but little more prominent than the walls 
of the reticulum into which they seem to run and disappear. The 
individual filaments themselves seem to be composed of fine granules 
and are, the writer thinks, quite surely threads and not plates. By 
carefully focusing above or below the blepharoplasts, irregularly 
arranged granules are seen which seem to indicate the thread-like 
nature of the radiations. These granules are interpreted as being 
cross sections of the kinoplasmic filaments. This, the writer is aware, 
is a disputed point in the structure of the kinoplasmic rays, and he 
has therefore very carefully examined many slides in the hope of being 
able to settle this question, at least in Zuma. The radiations are 
larger and coarser in Zama than in any other plant which has come 
under the writer’s observation, and it would seem to be a very favor- 
able subject for the study of such disputed points. The cytoplasm, 
viewed in cross or longitudinal section, presents the same irregular 
meshes, and while the writer is inclined to view this as a foam struc- 
ture, it is a point on which he has arrived at no very satisfactory 
conclusion. 
As the pollen tube apparatus continues to grow the blepharoplasts 
also increase in size, and about the first of April the contents, which 
stain red with safranin in the Flemming triple process, become more 
or less vacuolate (fig. 29). This occurs when the blepharoptasts have 
reached about halfythe diameter which they finally attain. During the 
general increase in size the kincplasmic rays have become more abun- 
dant and in many instances may be seen running from the blepharo- 
plasts out to the plasma membrane of the cell with which they seem 
to connect. 
GROWTH OF BASAL END OF POLLEN TUBE. 
The entire prothallial apparatus continues to increase in size until 
about the middle of May in Z. flortdana and the first of June in 
Z. pumila, when the central cell and blepharoplasts have reached their 
full size and the preparation for their division begins. The pollen 
tube, which has been gradually increasing in length and diameter, has 
now reached the extent of its growth in the tissue of the nucellus and 
has become more or Jess gorged with starch and reserve food materials. 
The tubes, of which there are commonly from 4 to 8 and sometimes as 
high as 13 or 14 in a single nucellus, usually grow to a length of 
24 to 4 mm. and are from 80 to 150 4 in diameter in the tissue of the 
nucellus. They are ordinarily unbranched, but occasionally a branched 
tube is observed. The writer has never observed an instance where a 
tube had branched more than once. At this period of development, 
and later until fecundation takes place, the pollen tubes can be plainly 
seen in an examination of the apex of the nucellus with the unaided 
eye. The tissue next to the tubes is brownish or yellowish, clearly 
marking the path of the tube. Furthermore, the tube usually causes 
5526—No. 2—01——3 
