40 OUR NATIVE FERNS AND THEIR ALLIES. 



1 06. Salvinia (Fig. 30), more often seen in cultivation, 

 has the sporocarps borne in clusters on short branches of the 

 floating stem, one or two of each cluster bearing ten or more 

 macrosporangia, each of which contains a single macrospore, 

 the remainder bearing numerous globose microsporangia with 

 numerous microspores. 



1 07. Germination. — In Marsilea the antherozoids are 

 produced in a rudimentary prothallium which develops from the 

 microspore and are corkscrew-shaped, consisting of several 

 coils. The prothallium, developed from the apex of the ma- 

 crospore is a hemispherical mass of tissue, and contains a sin- 

 gle archegonium. Much is yet to be learned of the habits and 

 life-history of our native species. 



LITERATURE. 



Andrews (W. M.). Apical growth in roots of Marsilia 

 qi{adrifolia and Equisetum arvense. In Botanical Gazette, XV, 

 174-177 (1890). 



Baker (J. G.). Fern Allies, pp. 134-149 (1887). 



Braun (Alexander). On the North American species of 

 Isoetes and Marsilia. In Silliman's JourJial, Second Series, 

 III, 52-56 (1847). 



\Jeb&r MarsiliannAPihtlaria. \nMonatsb.der Kiinigl. 



Akad. der Wissenschaft, 1863, 413-436; 1870, 653-753; 1872, 

 635-679. 



Campbell (D. H.). The systematic position of the Rhizo- 

 carpeae. In Torrey Bulletin, XV, 258-262 (1888). 



The development of Pilularia globulifera L. In An- 

 nals of Botany, in. 233-264, pi. xill-xv (1888). 



On the Prothallium and Embryo of Marsilia vestita. 



In Proc. Cal. Acad. Science, III, 183-205, pi. Ill, IV (1892). 



Some notes on Azolla. In Zoe, iii, 340-343 (1893). 



The development of the Sporocarp of Pilularia Ameri- 

 cana A. Br. In Torrey Bulletin, XX, 141 -148, pi. CXLVI (1893). 



Engelmann (George). New Species of j¥ar.rz7za. In Silli- 

 man's Journal, Second Series, vi (1848). 



Strasburger(L.). \]ebe.T Azolla. 8vo, 7 plates. Jena (1873). 



Underwood (L. M.) and Cook (O. F.). Notes on the 

 American Species of Marsilia. In Torrey Bulletin, xiv, 89-94 

 (May, 1887). 



