
RECENT INVESTIGATIONS UPON THE EMBRYO 
SAC OF ANGIOSPERMS. 
DOUGLAS HOUGHTON CAMPBELL. t] 
THE development of the embryo sac of the angiosperms has 
engaged the attention of many botanists from Hofmeister on, 
and the homologies of its parts have been widely discussed. 
All of the earlier researches seemed to indicate an extraordinary 
uniformity in the structures of the embryo sac, very few devia- 
tions from the type being noted, and the importance of these 
variations being frequently ignored. 
With the improved histological methods developed in recent 
years there has been a renewed interest in the subject. The 
important paper by Treub on Casuarina! called attention to 
several striking deviations from the ordinary angiospermous 
type. This paper was followed by a long series of investiga- 
tions by many botanists both at home and abroad, which have 
extended materially our knowledge both of the morphology and 
physiology of the embryo sac. 
The uniform results of the earlier investigations may be 
explained, in part at least, by the selection of the more special- 
ized forms for study. These would naturally conform, for the 
most part, to the structure characteristic of the embryo sac of 
the typical angiosperms. The more generalized and presum- 
ably more primitive forms were neglected, and the significance 
of such important variations as the largely increased number of 
antipodal cells in many grasses was usually overlooked. So 
great, indeed, was the uniformity assumed to be, that all efforts 
to explain the origin of the angiosperms from lower forms was 
considered well-nigh hopeless. 
The studies of the last dozen years have shown that there is 
much more deviation from the type than was supposed to be the 
1 Sur les Casuarinées et leur place dans le systéme naturel, Annales du Jardin 
Botanique de Buitenzorg, tome x, pp. 143-231. Leyden, 1891. 
: 777 
