SPEEMAPH YTES : PH^NOGAMS. 133 



resumed in the spring, the flower (cone) increases rapidly in 

 size and becomes decidedly green in color, the ovules increas- 

 ing also very much in size. If a scale from such a cone is 

 examined about the first of June, the ovules will probably 

 be nearly full-grown, oval, whitish bodies two to three milli- 

 metres in length. A careful longitudinal section of the scale 

 through the ovule will show the general structure. Such a 

 section is shown in Figure 77, G. Comparing this with the 

 sporangia of the pteridophytes, the first difference that strikes 

 us is the presence of an outer coat or integument (in.) 9 which 

 is absent in the latter. The single macrospore (sp.) is very 

 large and does not lie free in the cavity of the sporangium, 

 but is in close contact with its wall. It is filled with a color- 

 less tissue, the prothallium, and if mature, with care it is 

 possible to see, even with a hand lens, two or more denser 

 oval bodies (ar.), the egg cells of the archegonia, which here 

 are very large. The integument is not entirely closed at the 

 top, but leaves a little opening through which the pollen spores 

 entered when the flower was first formed. 



After the archegonia are fertilized the outer parts of the 

 ovule become hard and brown, and serve to protect the embryo 

 plant, which reaches a considerable size before the sporangium 

 falls off. As the walls of the ovule harden, the carpel or leaf 

 bearing it undergoes a similar change, becoming extremely 

 hard and woody, and as each one ends in a sharp spine, and 

 they are tightly packed together, it is almost impossible to 

 separate them. The ripe cone (Fig. 75, A) remains closed 

 during the winter, but in the spring, about the time the flowers 

 are mature, the scales open spontaneously and discharge the 

 ripened ovules, now called seeds. Each seed (E, s) is sur- 

 rounded by a membranous envelope derived from the scale to 

 which it is attached, which becomes easily separated from the 

 seed. The opening of the cones is caused by drying, and if 

 a number of ripe cones are gathered in the winter or early 

 spring, and allowed to dry in an ordinary room, they will in 



