PINES (PINACEAE) 



451 



maining portion of the nucellus hardens, so that the seed when 

 mature resembles some of the stone fruits, such as the' Plum, 

 although it is a seed and not a fruit. 



It is obvious that a seed is simply a transformed megaspo- 

 rangium. In the Cycads a seed is a megasporangium which has 

 its outer portions modified for protection and contains within 

 a female gametophyte bearing a 

 young sporophyte. Thus the re- 

 duction of the female gametophyte 

 through the Pteridophytes and 

 finally its retention in the mega- 

 sporangium in the Cycads so that 

 the young sporophyte also develops 

 within the megasporangium were 

 important steps in the evolution of 

 the seed. 



<- Although the Cycads resemble 

 Ferns in having swimming sperms, 

 and in having leaves and stems that 

 are Fern-like, they contrast with 

 them in such new features as differ- 

 entiation of strobili, simpler ga- 

 metophytes, pollination, growth of 

 pollen tubes, and the seed. 



Pines (Pinaceae) 



The Pines are a subdivision of the 

 Pine family (Pinaceae) . In addition 

 to the Pines, the Pine family in- 

 cludes the Spruces, Firs, Hemlocks, 

 Larches, Cedars, Redwood, Cypress, 

 and others. The Pine family is an 

 exceedingly important one because it includes a large proportion 

 of the trees from which lumber is obtained. The Pine family 

 belongs to the order of Conifers (Coniferales), so named because 

 of the cones which they bear. Not all of them, however, bear 

 dry cones like the Pines, for some have fleshy fruit-like structures, 

 as the berry-like structures of the Junipers illustrate. All of the 

 representatives of the Pine family are interesting, but a study of 

 their life history will be limited to that of the Pine. 



FIG. 400. Pine sporophytes. 

 After Miss Hay den. 



