1913] YORK—DENDROPHTHORA 213 
2 nuclei present in the chalazal end of the 4-nucleate sac. The 2 
polar nuclei are sister nuclei and are derived from one of the 2 
nuclei present in the micropylar end of the 4-nucleate sac. The 
nuclei of the egg apparatus arise from the sister nucleus of the one 
from which the polar nuclei are derived. 
The nuclei of the 2, 4, 7, or 8-nucleate stages of the embryo 
sac are apparently formed amitotically. 
Pollination does not occur. 
An embryo is formed in only one of the two sacs in each flower. 
In D. opuntioides the egg nucleus gives rise to a mass of tissue, the 
proembryo. From a central cell of the proembryo the embryo 
develops. The endosperm is derived from the remaining cell of 
the proembryo. | 
The embryo is regarded as pseudo-apogamous in origin. 
In D. gracile the ‘polar nuclei”’ fuse and give rise to a proembryo 
quite similar to that in D. opuntioides. The embryo and endo- 
sperm arise in the same manner as in the latter. 
The embryo is strictly dicotyledonous and is almost entirely 
imbedded in the endosperm. 
Apparently there is no chromosome reduction preceding the 
formation of the megaspores in D. opuntioides, while in D. gracile 
this process does seem to occur. In the latter, the diploid number 
of chromosomes is restored at the fusion of the “polar nuclei.” 
Brown UNIVERSITY 
PROVIDENCE, RHODE ISLAND 
LITERATURE CITED 
1. BaILton, M. H., Recherches organogéniques sur la fleur femelle de 
lV’ Arceuthobium Oxycedri. Assoc. Franc. Clerm. 1876. 
2. Biackman, V. H., On the fertilization, alternation of generations, and 
general cytology of the Uredineae. Ann. Botany 18:323-373. pls. 21-24. 
1904. 
3- Braver, A., Zur Kenntniss der Reifung des parthenogenetisch sich 
entwickelnden Eise von Artemia salina. Abh. Preuss. Akad. Wiss. 1893. 
4. Day, D. F., Parthenogenesis in Thalictrum Fendleri. Bot. Gaz. 22: 241. 
1896. 
5. DeBary, A., Uber Apogamie Farne und die Erscheinung der Apogamie 
im Allgemeinen. Bot. Zeit. 36:450-495. 1878. 
