Studies in Nuclear Division of Preissia commutata. 1 
BY 
MARGARET GRAHAM. 
With Plates LIV and LV. 
I N the gorges and smaller ravines in the vicinity of Ithaca there are 
many places where the water, dripping almost constantly over the 
rocks, affords favourable environment for the development of various species 
of Liverworts. While studying the morphology of the Bryophytes, my 
interest in the Liverworts that grew here first began. In an effort to learn 
more about one of them which is very abundant near Ithaca, this piece of 
work was undertaken. 
Material for the study of the vegetative cells was collected from several 
localities. During July, 1910, plants were sent twice a week from Coy 
Glen, near Ithaca, and kept in good growing condition on the bank of 
a brook in Mount Vernon, New York. Other material was collected during 
July and August, 1911, in Buttermilk Gorge and Enfield Gorge, in the 
vicinity of Ithaca, and the material fixed in the laboratory. The plants 
sent to Mount Vernon and those collected in Buttermilk Gorge were equally 
satisfactory for the study of somatic division. 
I. Mitosis in the Vegetative Cells. 
(Plate LIV.) 
Cells on or near the dorsal surface of the thallus of Preissia commutata 2 
contain so many metaplasmic bodies, such as granules, plastids, starch, &c., 
that it is difficult to make a careful examination of the cytoplasm and 
nucleus for the presence of certain structures, especially centrospheres and 
centrosomes, which have been found in some Liverworts. A region almost 
free from the above-mentioned bodies was found on the ventral side of 
the thallus, just behind the turn made by the upward growth of the 
gametophore. 
1 Contribution from tbe Department of Botany, Cornell University, No. 154. 
2 Portions of thalli were killed in Flemming’s fluids, the stronger, medium, and weaker solutions; 
in Merkel’s fluid, and in chromacetic solution. The Flemming’s fluid, weaker solution, gave the 
best results. Air was pumped out of all tissues after being placed in the killing fluids. Sections 
were cut 5 ^ in thickness. 
[Annals of Botany, Vol. XXVII. No. CVIII. October, 1913.] 
