CONIFERALES 



357 



Even before fertilization, the stony layer of the testa has begun 

 to develop (fig. 341). At this time three layers are recognizable, the 

 outer and inner fleshy layers, with the stony layer between them. 

 The cells of the stony layer interlock somewhat, but they do not in- 

 tertwine as in the cycads. Their walls become thicker as their cell 

 contents disappear. The inner fleshy layer may be considered as 



.,.KfflT''»^^ 



s -V - iStony /o^en. 

 JQA. Inner fleshij kyen 



/7egQ spore 

 ,,4P — fffembrane... 



^ Female 

 l^^.qamefophtfte^. . 



A 



Fig. 341. — Finns laricio: A, young seed at time of fertilization; B, nearly ripe seed. 

 The inner and outer layers have nearly disappeared. 



made up of all the tissues between the stony layer and the female 

 gametophyte. 



In the cycads, the outer fleshy layer usually becomes variously 

 colored, with red, orange, or cream colors predominating; this outer 

 coat persists for a long time, finally drying and becoming very tough 

 and leathery. In conifers, it is seldom colored while it is young and 

 fleshy. Later, it becomes brownish and very thin, and may disap- 

 pear entirely, so that the stony layer is the outer layer of the seed. 



The inner fleshy layer, at the time of fertilization, is the thickest 



