and Laboratory Methods. 2625 



3. Observe fresh or dried, young cones and note the presence of a special 

 color. How do you account for the color in this cone ? 



(f ) Gametophytes and seed. 



The gametophytes of Phiiis laricio may be studied from staminate and car- 

 pellate cones preserved in alcohol. The seeds may be kept in a dry condition. 



1. Draw a male gametophyte (pollen grain) under high power. Note the 

 two wings. These represent an adaptation for anemophilous pollination. 



2. Remove a female gametophyte from a young seed and draw under dis- 

 secting microscope. Note the difference in size between the male and female 

 gametophytes. Compare the two gametophytes with those of Marsilea and 

 Selaginella. 



3. From the female gametophyte of a mature seed carefully cut out the 

 embryo sporophyte, which is now in a dormant condition. Sketch under dis- 

 secting microscope, showing the radicle and cotyledons. Pick off the cotyledons 

 from one side and sketch the plumule. How many cotyledons ? 



4. If prepared slides are at hand draw a section of a stamen, showing the 

 one-celled microspores. 



5. Draw a section of a male gametophyte, showing the large tube cell and 

 nucleus, the generative cell and the two disorganized vegetative cells lying like 

 two thin plates against the wall of the grain back of the generative cell. 



6. Draw a section of a young ovule, showing the functional megaspore. 



7. Draw a pollen grain which has formed a short pollen tube growing down 

 into the nucellus (tip of the megasporangium). Note the tube nucleus in the 

 tube and in the body of the grain the spermatogenous cell, the stalk cell and the 

 remains of the two evanescent vegetative cells. The spermatogenous cell divides 

 later into two sperm cells which do not have flagella or cilia. From the same 

 section draw the spherical embryonic female gametophyte. 



8. Draw a female gametophyte showing archegonia with oospheres. 



9. Draw an archegonium in which the nucleus of the oosphere has divided 

 into four nuclei. 



10. Draw the upper part of a female gametophyte, showing remains of 

 archegonia with an elongated cavity below them in which appear a number of 

 embryos in various stages of development. Only one of these embryos survives, 

 probably the one which has a slight advantage in size, vigor, and food supply. 

 Note the struggle for existence which must go on among these embryos. 



11. Sketch a mature seed, showing the wing. Let a winged seed drop to the 

 floor from a height of six or seven feet and note how it falls. Describe the 

 adaptation this seed has for dissemination. Note also the readiness with which 

 the seed is separated from the wing. Of what use is this adaptation ? 



(g) Seedlings and Primitive Leaf Arrangement. 



Plant seeds of Pinus and Thuja occidentalis and use fresh plantlets or pre- 

 serve in alcohol. Also obtain branches of the common juniper (Juniperns com- 

 munis L. Family, Juniperaceae) and cultivated varieties of Thuja known as 

 retinispora forms. In these retinispora or juvenile forms, branches often change 



