PEANEBOGAMIA. 223 



(J) Split a staminate and an ovule-bearing cone vertically, and 

 study their structure, comparing the one with the other. Dissect 

 out a stamen and an ovule-bearing scale, and compare. In the 

 former note the pollen-sacs, and in the latter the ovules (Pigs. 120 

 and 122). 



(c) Study pollen-cells from young and mature staminate cones. In 

 the young pollen look for the cells representing the first stage (pro- 

 thallium); in the ripe pollen note the bladder-lilse enlargements of the 

 outer coat (Pig. 121, E). 



(d) Note that the ovule-bearing cones of Scotch and Austrian pines 

 are two years in coming to maturity. Make vertical sections of cones 

 of various ages, and note the growth of the seed. Note the thin 

 wing (useful in their dispersion) on the seeds. Make longitudinal 

 sections of seeds, and note the little plantlet with its several kavea 

 (cotyledons). 



(«) Make cross-sections of leaves, and note the turpentine-canals, 

 one near each angle, with others symmetrically arranged between. 

 Make cross-sections of the young twigs, and note the canals in the 

 rind or bark. Make similar sections of the wood of the trunk, and 

 note similar canals at intervals. 



(/) Make very thin cross-sections of the mature wood of the stem, 

 and note shape and size of the cells; note also the gradual decrease 

 in the size in passing from the inner to the outer side of a growth- 

 ring. Now make a very thin longitudinal-radial section, and observe 

 the bordered pits (Fig. 126). A longitudinal section at right angles 

 to the last (longitudinal-tangential) will show no bordered pits. In 

 all these sections note that the wood is made up of but one kind of 

 cells, viz., tracheids. 



(g) In a cross-section of a stem, note the thin radiating plates of 

 tissue (medullary rays), in many cases extending from pitli to bark. 

 In longitudinal-tangential section of the stem these rays are seen in 

 cross-section to be made of thick-walled cells (stony tissue). In longi- 

 tudinal-radial sections the rays are seen split lengthwise (Fig. 126, sQ. 



(Ii) Make very thin cross-sections of the stem through bark and 

 wood, and note the layers of very soft thin-walled tissue (cambium) 

 between wood and bark. This may be made more evident by soak- 

 ing the section for a few hours in carmine, by which the cambium 

 will be stained. 



There are three orders of Gymnosperms, viz.: 

 472. The Cycads (Order G^/eadaoece) are large or small 

 trees, with much the general appearance of the palms and 



