53° Reed . — The Value of Certain Nutritive Elements 
and, perhaps, from the neighbouring cells, necessary for their existence and 
growth. The more sluggish nuclei of the incipient female sex cells being 
unable to obtain the necessary substances for growth and activity, did not 
develop far enough to form sexually mature cells. 
Some instructive facts upon the role of calcium salts were obtained 
by studying the process of cell-division in filaments of Spirogyra in 
calcium-free solutions. The conventional method of submitting the cultures 
to a low temperature during the night in order to stimulate mitotic division 
was adopted. Cultures of Spirogyra which had grown for six weeks without 
calcium salts showed evidences of some injury, yet the nuclei were able 
to divide. The mitosis was found to be in progress in many cells one hour 
after the cultures were removed from the refrigerator. Three hours and 
forty minutes after removal from the refrigerator I found many instances 
of mitosis, some of which were approaching completion. So far as the 
substance of the nuclei themselves was concerned, the mitotic divisions 
appeared to be typical, but the new transverse cell-wall was frequently 
incomplete, and still more frequently was entirely lacking. The appearance 
of the cells closely resembled those described by Molisch (’95) under 
similar conditions. In the control cultures the mitoses were normal and 
had formed perfect cell-walls between the daughter nuclei. 
In the growing region of the root, a similar effect upon the process of 
mitosis was noted. Stained sections of the roots of Zea Mais plants, which 
had grown in calcium-free solutions, showed a number of cases in which the 
transverse septum had not formed after the process of nuclear division was 
completed. 
A similar incapacity to form cellulose was found in the case of an alga 
which was about to form the thick walls of the resting spore. A quantity 
of Spirogyra was in the initial stages of conjugation when put into cultures 
on June 30. On July 13, when I examined the cultures I found that many 
of the filaments in the calcium-free solutions had succeeded in forming 
normal conjugating tubes, and that gametes had been produced. The most 
striking feature that I found was the case of conjugating cells which had 
fused to form a resting spore, but no cellulose wall was formed upon the 
surface of the plasmatic mass. In other respects the process of conjugation 
appeared to be normal, and I cannot explain the lack of cellulose forming- 
power unless it be caused by the lack of calcium salts. 
The absence of calcium has been observed by several investigators 
to have a similar effect upon the power of the cell to form cellulose. It 
seems possible that some light might be shed upon the question by a 
consideration of the nature of the framework upon which the cell-wall 
is built. The middle lamella, as was first shown by Payen (’ 46 ), is composed 
of calcium pectate. Timberlake (’ 01 ) showed that the middle layer which 
appears after the splitting of the cell-plate in the later stages of mitosis may 
