THE MEGASPORANGIUM 



77 



in Elytranthe (Schaeppi and Steindl, 1942), Langsdorffia (Fagerlind, 

 1945a), and Balanophora (Fagerlind, 19456) (Fig. 53 A-F) the micro- 

 pylar megaspore gives rise to the embryo sac and the other three 

 soon degenerate. A similar condition occurs in the Onagraceae 

 and in a few members of the Compositae, although here it is not 

 unusual to find both the terminal megaspores, micropylar and chala- 

 zal, growing concurrently (Fig. 53ilf,iV). In Rosa (Hurst, 1931) 





Fig. 54. Formation of megaspore haustoria in Galium lucidum (A-C), Sedum 

 sempervivoides (D), and Rosularia pallida (E). (A-C after Fagerlind, 1987; 

 D-E after Mauritzon, 1933.) 



it is usually the micropylar megaspore which functions (Fig. 532£) 

 but sometimes it is the second (Fig. 53L). In Aristotelia (Maurit- 

 zon, 1934), belonging to the Elaeocarpaceae, it is the third mega- 

 spore from the micropylar end which gives rise to the embryo sac 

 (Fig. 53 J"). Rarely, as in Gloriosa (Afzelius, 1918; Eunus, 1949) 

 (Fig. 53G-I), Ostrya (Finn, 1936), Poa (Hakansson, 1943), and 

 Casuarina (Swamy, 1948) (Fig. 51) all or any of the four megaspores 

 may begin to enlarge and divide. A peculiar condition occurs in 

 Rosularia, Sedum (Mauritzon, 1933), Laurus (Bambacioni-Mezzetti, 



