90 MARGARET C. FERGUSON 



mother-cell, but there is no evidence from the standpoint of origin 

 that such is the case in Pinus. They arise directly from a nucel- 

 lus in which a few days before their appearance every cell was 

 apparently like every other cell. This alone is not conclusive, 

 as the functional macrospore-mother-cell has a similar origin, so 

 far as one can see. But, what is more conclusive, the divisions 

 in this tissue are according to the typic method and present the 

 number of chromosomes characteristic of the sporophyte (figs. 

 164-167). If these cells were once, in some remote ancestor, 

 sporogenous in nature, they have entirely lost their primitive 

 function and have acquired a new and important function in 

 connection with the development of the endosperm. This is 

 not then a layer of disintegrating tissue, as described by all 

 earlier students of the AbietinccB, but rather as alread}'^ noted 

 by the writer (1901^) a definite zone of physiological tissue 

 which is intimately connected with the nutrition of the young 

 gametophyte. It doubtless not only passes on to the endosperm 

 the nutrititive substances derived from the nucellus, but is itself 

 active in the manufacture of food, as numerous starch grains 

 are often found within its cells. It is probable, too, that it 

 performs an important mechanical role in the wa}^ of protection. 

 It not only forms a support for the prothallium in its multinu- 

 cleated state, but gradually receding, it pushes before it, as it 

 were, the tissue of the nucellus thus making room within for 

 the growth of the delicate gametophyte. 



Though we now know that this is a far more important tissue 

 than it was formerly thought to be, it does not seem to me wise to 

 apply to it the name tapetum or to suggest a new name by which 

 to designate it. Strasburger's term " spongy" tissue, although 

 given when the nature of this tissue was not understood and 

 being a misnomer so far as its structure and function are con- 

 cerned, has obtained a wide usage in the literature of the Gym- 

 nosperms, and should be retained, just as the term cell is still 

 retained in all biological literature. 



DEVELOPMENT OF THE ARCHEGONIUM. 



The Ea7'ly Grozvih of the A?'chci>-o)iii(i)i. — The archegonia 

 first become apparent during the latter part of May or the very first 



