272 
METHODS IN PLANT HISTOLOGY 
cell, a generative cell, and a tube cell. For preparations at the 
shedding stage, shake the cone over a piece of paper and pour the 
pollen into water. After 15 or 20 minutes, put it into the fixing 
agent. In wind-pollinated plants, the pollen would look shriveled 
if you put it into a fixing agent before it regained its turgidity. 
The pollen, mounted whole, makes beautiful preparations. Fix 
in formalin-acetic acid (formalin 10 c.c., acetic acid 5 c.c., water 
Fig. 94.— Ceratozamia mexicana: A, pollen grain which has been in a sugar solution for 
two days; X876; B, nucellus with numerous pollen tubes; X17; C, basal end of pollen tube 
showing the persistent prothallial cell; outside it the stalk cell; and, above, the two sperms still 
inclosed in the sperm mother-cells; X156. 
100 c.c.). Stain in iron-alum haematoxylin and follow the Venetian 
turpentine method. Carmalum, as described in the Power’s methods 
on page 178, is also satisfactory. If some material is put into a 
5 or 10 per cent sugar solution for two or three days, early stages in 
the formation of the pollen tube may be added. In a week or two 
the tubes may reach several times the length of the pollen grain; 
but, as far as we know, the generative cell has never divided in culture 
solutions (Fig. 94A). 
