MORPHOLOGY 19 



In many details the ovules correspond to sporangia, 

 but they are not simply sporangia, and they have added 

 to them several coats and inner tissues which no simple 

 sporangium has. The egg-cell, however, is the funda- 

 mentally important feature in them, and it is with this 

 cell that the male nucleus fuses, and it is for the sake 

 of bringing these two cells together, and protecting the 

 young embryo formed after their fusion, that all the 

 complexity of the flower has been developed. How 

 complex it is, and how ancient its history, one can only 

 realise after studying the fossil types which have gradu- 

 ally led up to it. 



Some of the fossil seeds from the Coal Measure period 

 are even more complex than those of the present day. 



We have now noticed shortly all the organs of a plant. 

 It is likely that a reader will immediately think of fruits 

 and seeds which appear such distinctly characteristic 

 structures. They are, however, but modifications of 

 the parts we have already mentioned. The seeds are 

 but the ovules enlarged with the growing embryos, 

 in their tissues storehouses of food, and with the 

 outer ovular coats hardened. The fruit, whether fleshy, 

 winged, or plumed, is a further growth and modifica- 

 tion of the carpel leaves or of several carpel leaves 

 fused together, or of the carpels with some of the other 

 flower-parts adhering to it and ripening with it, instead 

 of being shed as soon as the flowering was done. The 

 only new thing in the fruits and seeds is the embryo, 

 and that begins a new cycle and belongs to a new 

 generation. It is composed, however, of the funda- 

 mental vegetative organs a root, a stem, and the first 

 leaves. These organs are produced in miniature in 

 the seed, and then they lie there for a long resting 

 period in most plants. 



