2622 Journal of Applied Microscopy 



phytes and the lower seed plants is that in the latter the microspores and mega- 

 spores are not shed, but develop the male and female gametophytes in the micro- 

 sporangia and megasporangia respectively, while in the former the spores drop 

 to the ground. The female gametophyte remains permanently enclosed in the 

 megasporangium, but the male gametophytes are shed from the microsporangia 

 and some fall into the micropyle of the ovule. This is known as pollination. 

 In order that the spermatozoids may fertilize the oospheres in the archegonia a 

 short pollen tube must grow through the tissue between the pollen chamber and 

 the female gametophyte. It will be observed that the gametophytes are now 

 entirely parasitic, the female in the ovule and the male at first in the pollen sac 

 and, after pollination, in the wall of the ovule. 



LXXII. Ginkgo biloba L. Maiden-hair Tree. 



Class and order, Ginkgoales. Family, Ginkgoaceae. 



This beautiful tree, a native of China and Japan, is cultivated quite exten- 

 sively in the United States. Museum and herbarium material may be used. 



Sporophyte. 



1. Sketch a leafy branch, showing the leaves developed in clusters on dwarf 

 branches. Note that dwarf branches may give rise to ordinary branches. 



2. Sketch a single leaf under dissecting microscope, showing the dichoto- 

 mous venation. Compare the venation with that of the Adiantum leaf. 



3. Sketch a stamen (microsporophyll) under low power. How many micro- 

 sporangia or pollen sacs ? Compare with stamen of Cycas. 



4. Sketch a mature fleshy seed on its long stalk. Note the collar or cup 

 around the base of the seed and the small undeveloped ovule. On some stalks 

 two seeds develop. Remove the fleshy part of the integument and note the 

 hard, inner layer. 



Gametophyte. 



5. Draw a male plant (pollen grain) under high power. 



6. From alcoholic material study the mature female gametophyte (kernel of 

 of the seed). Sketch, and compare the size of the male and female gameto- 

 phytes. 



7. Carefully cut longitudinal sections from one side of the female gameto- 

 phyte until the embryo sporophyte comes into view, and sketch the section under 

 dissecting microscope, showing the embryo in position. 



LXXIII. Conifers. General Study. 

 Class, Coniferae. Order, Finales. 



The conifers called for below are cultivated quite extensively, and material 

 for study can usually be obtained without difficulty. 



(a) Finns. Family, Pinaceae. 



Collect large branches of white pine {Finns sirobus L.), pitch pine (F. rigida 

 Mill), Austrian pine {P. laricio Poir.), and Scotch pine {P. silvestris L.). Also 

 collect the dwarf branches with needle-leaves which have been self-pruned. 



