370 BOTANICAL GAZETTE [may 



of all the genera, it seems wiser to reserve theoretical considerations 

 until the available evidence has been examined. 



Summary 



i. Stangeria is probably monotypic, with S. paradoxa as its 

 single polymorphic species. 



2. At fertilization there is a pairing of chromosomes resembling 

 the pairing in the heterotypic mitosis, so that the number during 

 the metaphase of the first division is apparently haploid, although 

 really diploid. 



3. There are two free nuclear periods in the embryogeny. the 

 hrst comprising 9 or 10 simultaneous mitoses and extending through- 

 out the proembryo, and the second with only 2 or 3 mitoses and 

 confined to the lower part of the proembryo. The embryo and 

 suspensor are formed from the second series. 



4. There is an evanescent segmentation of the entire egg. as 

 in Dioon. 



5. The young embryo is very narrow and its haustorial struc- 

 tures are more conspicuous than in any other cycad yet described. 



6. Polarity, which may appear even at the beginning of embry- 

 ogeny, becomes more and more marked as development proceeds. 



University of Chicago 



LITERATURE CITED 



1. Treub, M., Recherches sur les Cycadees. 3. Embryogenie du Cycas 

 circinalis. Ann. Jard. Bot. Buitenzorg 4:1-11. p/s. 1-3. 1884. 



2. Lang, W. H.. Studies in the development and morphology of cycadean 

 sporangia. I. The microsporangia of Stangeria paradoxa. Ann. Botany 

 11:421-438. pi. 22. 1S97. 



3. Ikeno, S., Untersuchungen iiber die Entwickelung der Geschlechtsorgane 

 und der Vorgang der Befruchtung bei Cyias revoluta. Jahrb. Wiss. Bot. 



32:557-602. pis. S. Q. 1898. 



4. Worsdell, \Y. C, The vascular structure of the sporophylls of the Cyca- 

 daceae. Ann. Botany 12:203-241. pis. 17, 18. 189S. 



5. Lang, W. H., Studies in the development and morphology of cycadean 

 sporangia. II. The ovule of Stangeria paradoxa. Ann. Botany 14: 

 281-306. pis. 17. 18. 1900. 



6. Webber, H. J., Spermatogenesis and fecundation of Zamia. Bull. no. 2. 

 Bur. PI. Ind., U.S. Dept. Agric. pp. 100. pis. 7. 1901. 



