THE MEGASPORANGIUM 



59 



bus, and Cydonia, indicating that this is the prevailing tend- 

 ency among the Rosaceae. In 1882 Guignard 17 added Erio- 

 botrya to the list, and in 1901 Murbeck 57 found an archesporial 

 group in Alchemilla alpina. Recently, however, Pechoutre 63 

 has made a general survey of the Rosaceae, and in all of the 

 fourteen genera studied, well distributed among the tribes, there 

 was found a many-celled archesporium, showing a remarkable 

 persistence of this character throughout a large family. Among 

 the closely allied Saxifragaceae also, Webb 60 has found in 

 Astilbe this same type of archesporium. 



In 1891 Treub 23 published his account of Casuarina, re- 

 porting that the archesporium is a group of hypodermal cells, 

 and that the derived sporogenous tissue forms a large central 

 mass within the nucellus (Fig. 24). The account and the fig- 



Fio. 24. — Casuarina. Longitudinal sections of nucellus. A, section showing two pri- 

 mary sporogenous cells (shaded ) ; x 190. £, later stage showing extensive sporog- 

 enous tissue: x 190. C, pollen-tuhe (with heavier walls) among the elongated 

 sterile megaspores ; x 67. D, portion of nucellus at a much earlier stage than C, 

 showing numerous megaspore mother-cells ; x 157. — After Tkeub.* 3 



ures suggest that all of the sporogenous tissue may not be 

 derived from the hypodermal layer. In 1894 Miss Benson 28 

 discovered that a several-celled archesporium is present in Fa- 



