LIFE HISTORY OF PINUS IO3 



the ordinary nuclear reticulum, to nuclei which can scarcely be 

 distinguished from the surrounding cytoplasm, and then to arche- 

 gonia, which appear perfectly normal except that no nuclei can 

 be demonstrated within them. It is a well known fact, already 

 commented upon in this paper, that the number of seeds derived 

 from a pine cone is very small in comparison with the number 

 of ovules formed in the same cone. An examination of fresh 

 material shows that development may cease at any point be- 

 tween the early stages in the formation of the ovule and the last 

 steps in the ripening of the seed. This cessation of growth 

 effecting first individual cells does not at once become apparent, 

 and so cannot be avoided, in its earliest stages, when one is 

 putting up material for cytological work. Under such condi- 

 tions, it is inevitable that, with a limited amount of material, the 

 abnormal will be interpreted for the normal. 



The entire development of the archegonium in Pinus is passed 

 through in about two weeks, probably not more than five days 

 elapsing between the cutting off of the ventral canal-cell and 

 fertilization. In Pinus montana var. uncinata these processes 

 are apparently much more closely united in point of time, as 

 the pollen-tube, in some cases, has reached the endosperm 

 before the division of the central cell is complete (fig. 207, 

 plate XIX). 



The P}'oteid Vacuoles. — The true nature of the proteid 

 vacuoles is a subject which attracted my attention very early in 

 the course of these investigations. There can be no doubt that 

 there is an intimate relation between the sheath-cells of the 

 archegonia in the pines and the substance of the egg, such as 

 is believed to exist between the follicle-cells and the egg in ani- 

 mals. But the exact nature of this connection in Pinus is not 

 easily determined. I have rarely examined a preparation show- 

 ing archegonia without studying the relation of the sheath-cells 

 to the oosphere ; and yet no entirely satisfactory evidence, be- 

 cause not demonstrable beyond a question, of the origin and 

 nature of the so-called proteid vacuoles has been found. 



Hirase C9S) observed that the granules in the egg of Ginkgo 

 were of nucleolar origin, being derived both from the nucleus 

 of the central cell and from the nuclei of the sheath-cells. 



