468 BOTANICAL GAZETTE [DECEMBER 
groups of chromosomes enter the same nuclear membrane, but 
retain their former grouping; and (3) the chromosomes pair. The 
first is illustrated by the paired nuclei in Uredineae; the second by 
the chromatin groups during the first divisions of the Cyclops 
embryo; the third takes place soon after the fusion of the egg and 
sperm in Abies. It seems altogether probable that the chromo- 
somes do not actually pair until the prophase of the reduction 
division in such animals as Cyclops. There is a striking similarity 
between the pairing process as described in Abies and that con- 
cerned with tetrad formation in some animals (compare diagram A 
with diagram C). To what extent we are justified in suggesting 
that the processes are identical and that they are both concerned 
with the pairing of corresponding chromosomes from the egg and 
from the sperm, only further research can definitely determine. 
Relationships 
Abies, as compared with Pinus, shows a number of primitive 
characters: 
1. The male gametophyte: (a) an excessive polar (“‘prothallial’”’) 
tissue; (b) the equality of the male nuclei; both may function. 
2. The female gametophyte: (c) the large number of neck cells; 
as many as five tiers (Mryaki 19); (d) the persistence of the ventral 
canal cell; its nucleus may function as an egg nucleus. 
3. The ovulate strobilus and ovules: (e) the almost complete 
separation of scale and bract; (/) the development of a rudimentary 
pollen chamber; (g) the comparatively free integuments. 
4. The staminate strobilus: () the staminate strobili are borne 
on ordinary branches in the axes of ordinary leaves. 
5. The arrangement of leaves: (i) the spiral arrangement of 
leaves on ordinary branches (THOMSON 25; Lioyp 18). 
6. Vascular anatomy: (/) the general absence of ray tracheids 
(THOMPSON 26, 27), which in Pinus are present in the mature wood, 
but absent in the seedling and strobilus axis. 
It may be noted, however, that resin canals are not found in 
the woody axis of the Abies stem except as traumatic responses 
(JEFFREY 11). JEFFREY states that the presence of resin ducts is 
an ancient character which has persisted in Pinus. ‘On account 
