452 



SPERMATOPHYTES (SEED PLANTS) 



Sporophyte. The sporophytes of the Pines are mostly large 

 and in some cases are of huge dimensions. Some species of Pine 

 attain a height of 150 feet or more. It is characteristic of Pine 

 trees to have a main trunk and comparatively small lateral 

 branches. The main branches are usually in clusters, and in 

 some Pines, unless closely inspected, one might mistake the 

 branches to be in whorls. There is a gradual reduction in length 



of branches from below up- 

 ward, so that trees grown 

 in the open have a conical 

 shape (Fig. 400.) 



The needle-like leaves 

 are usually borne in groups 

 or fascicles of two, three, 

 or five leaves according to 

 the species. The duration 

 of leaves varies according 

 to the species and condi- 

 tions, but Pines shed only 

 a part of their leaves at a 

 time and hence are always 

 green. 



Strobili. The strobili, 

 as in the Cycads, are of 

 two kinds staminate and 

 ovulate (Fig. 401). The 

 staminate and ovulate 

 strobili occur separately, 

 on the same trees, or on 

 different trees. 



The staminate strobili or 

 cones (Fig. 402) are pro- 

 duced in clusters and in the Northern states may be seen in May or 

 early June. They vary in size in different species, sometimes at- 

 taining a length of half an inch or more, but in many species they 

 are much smaller. They expand from the buds in a few days, 

 soon shed their pollen and disappear, usually persisting only a few 

 weeks. A microstrobilus is, in reality, a modified branch con- 

 sisting of a main axis bearing scale-like microsporophylls or 

 stamens, which are arranged spirally and closely crowded. On 



FIG. 401. A branch of a Pine, show- 

 ing an ovulate strobilus at a and a cluster 

 of staminate strobili at 6. 



