STEUCTUEE OF THE SEED. 17 



VII. Dkvelopment of Ovules. 



Ill this examination the wall of the ovary must he reinoved, 

 and the minute eminences which are to become the ovules ob- 

 served in their earliest stage. The successive external produc- 

 tions which are to become the integuments of the ovule should 

 be traced with great care. It is also well to examine minutely 

 the clianges in form of the embi-yonal sac in the nucleus (or 

 nucelhis) of the ovule. These will be further adverted to under 

 " Fertilization." 



VIII. Minute Stuucture of the Seed. 



Since in the previous exercises some parts of the seed have 

 been alread3- examined, it is necessaiy here merely' to call atten- 

 tion to the desirability of studying the character of the integu- 

 ments in at least two common and a few exceptional cases. 

 For the former, no seeds are better than tliose of the common 

 Bean, Pea, or Lupine. After a clear idea lias been obtained of 

 the nature of the cells, which compose the greater part of the two 

 integuments, tlie student should make careful sections through 

 the hilura in order to display the peculiar sac-like body tliere 

 seen. For the exceptional types of integuments, examine the 

 seeds of Flax (showing the gelatinous modification, etc.), or 

 better, if tliej' can be procured, the seeds of CoUomia and Cot- 

 ton. It will be well also to examine tlie closely united ovarian 

 and ovular coats in the common grains, like Wheat or Indian 

 corn. 



The student should examine as many seeds as possible, includ- 

 ing those containing much, little, and no starch, and observe also 

 whether or not there is any difference between ripe and unripe 

 seeds in tlie amount of starch which tlie.y contain. He should 

 examine the contents of the cells nearest the integuments in any 

 of the seeds above mentioned, and ascertain the relative amount 

 of albuminoid matters present compared with those in the cells 

 in the interior of the seed. 



Further micr.oscopic examination of the seed is to be taken up 

 when germination is studied. 



