G YMNOSPERMS. 1 85 



the scales. Why are the cones and scales in these different positions at these 

 different times ? 



Remove several scales and study them carefully. Sketch the form of one 

 showing both sides. Upon the outer side note a small appendage (cover 

 scale ; if there are spruces at hand compare the difference in size of the 

 cover scale of the pine and spruce). 



Upon the inner side note the two oval bodies at the two lower angles. 

 These are the ovules, and correspond to the large sporangia. Note care- 

 fully a forceps-like appendage at the lower end of each ovule ; a little de- 

 pression between them. This is the place where the pollen is drawn up 

 after pollination. 



Observe that the seeds are developed at this same point on the scale, and 

 that the seed is formed from a later growth of the ovule and its parts. 



Observe also that the ovules and seeds of the pine are naked, that is, they 

 are exposed. From this character the name of the gymnosperms, or naked 

 seed plants, is derived. 



Exercise 59. 



303. The male cones.— Observe the large clusters of the male flowers, sev- 

 eral cones collected together. Sketch a cluster. Sketch a separate cone. Note 

 that the cone is made up of an axis and scales as in the female cone, but the 

 scales are different in form, Remove several of the scales. Note the form. 



Upon the under side note the two strong convexities. Cut across scale, 

 and note that there are two sacs situated here. These sacs are the spore- 

 cases (small sporangia). The fine granules which escape are the small 

 spores, or pollen. 



If you have an opportunity when the pollen is ripe on a pine tree, jar the 

 tree to see the clouds of pollen "dust " escape. When the sacs on the under 

 side of the scale open in drying, note the position of the slit. Sketch such 

 an open scale. 



Demonstration 43. 



304. Pollen grains. — Mount a few of the pollen grains in water for exam- 

 ination with the microscope. Let each pupil observe, and sketch a pollen 

 grain. Observe the two large air sacs on either side of the pollen grain. Of 

 what use are these air sacs to the pollen ? Do insects pollinate the pines, or 

 are they wind pollinated ? 



If it is desired to demonstrate the prothallium, archegonia, and fertilization 

 in the pine, the teacher can either prepare or purchase slides for the pur- 

 pose. See the author's larger "Elementary Botany," Chapters XXI and 

 XXII, for further studies of the gymnosperms, and for fertilization, etc. 



