284 
METHODS IN PLANT HISTOLOGY 
and there may be some doubt as to whether two such cells are always 
present. The division of the lenticular cell into “stalk cell” and 
“body cell,” and also the division of the body cell into the two male 
cells, must be looked for in sections of the nucellus of the ovule. 
Abies balsamea is a better type for illustrating spermatogenesis, 
since the pollen mother-cells and the pollen grains are much larger 
Fig. 100. —Abies balsamea: photomicrograph of pollen; one complete section showing two 
prothallial cells, the stalk cell, generation cell, and tube cell with starch grains. Fixed and cut 
while still within the microsporangium. Stained in safranin and gentian-violet. Eastman Com¬ 
mercial Ortho film, Wratten B filter (green); Spencer 4-mm. objective, N. A. .66; ocular X6; arc light; 
exposure, 6 seconds. Preparation by Dr. A. H. Hutchinson, negative by Dr. P. J. Sedgwick. X 784. 
and the division of the generative cell into the “stalk” and “body” 
cells takes place before the pollen is shed (Fig. 100). 
Araucaria and Agathis are the best forms for illustrating numerous 
prothallial cells/ Podocarpus and Taxodium are also good. Thuja or 
Juniperus may be used to illustrate the entire absence of prothallial 
cells, a very advanced condition; while both these genera have highly 
developed sperms, like those of the cycads and Ginkgo, except that 
they lack cilia. This is a good illustration of the fact that one 
structure may advance while another remains primitive. 
