STRUCTURE.] FORMATION OF ALBUMEN. 55 



a combination of both. It may be sometimes formed from 

 each. In the process of growth the embryo-sac becomes filled 

 with cellular tissue, which produces the albumen. Examples 

 may be seen in Philydrum lanuginosum, also in all Arads, 

 Grasses, Sedges, Lilyworts, Palms, &c. Amomals are an 

 exception, for excepting Canna, they develop their albumen 

 in the nucleus, as in Maranta gibba. The development of 

 Canna is altogether peculiar. The albumen is developed in 

 the region of the chalaza, and although five layers can be dis- 

 tinguished they can none of them be identified. In Dicoty- 

 ledons the growth of the albumen is not so uniform, in these 

 whole groups of families being characterised by its presence or 

 absence. The albumen formed in the embryo-sac is called 

 Endosperm, while that formed in the nucleus is called Peri- 

 sperm. When the embryo-sac does not fill the nucleus, and 

 the embryo does not fill the former, both perisperm and endo- 

 sperm are developed, as seen in Waterlilies (Nymphaeaceae) 

 and Watershields (Hydropeltideae) ; also in Peppers. In Che- 

 lidonium majus, the endosperm is alone developed ; and this 

 is the case with all Papaveraceae, Ranunculaceae, Umbelli- 

 fers and Cinchonads. The perisperm is probably developed 

 in all families which have what is called albumen centrale. 



2. On the Structural Relations and Extent of the Albumen. 

 In most cases the albumen has the form of the seed on a re- 

 duced scale. A remarkable deviation is seen in Convolvulus. 

 The endosperm consists of a double spindle-shaped body, 

 with two wing-like appendages, between which the cotyledons 

 are placed. In many of the Figworts (Scrophulariacea3) the 

 embryo-sac forms little cavities or bags, which, in the ripe 

 seed, remain as appendages to the albumen. Albumen, as 

 well as all other parts of plants, consists essentially of cellular 

 tissue, the cells of which have contents. Cytoblasts are found 

 only occasionally in the cells of albumen, but may be seen 

 very well in Zea Mays. The cells present all the varieties of 

 ordinary parenchym, but never any spiral structure. The 

 walls of the cells are generally thin, simple, without evident 

 configuration, as in the case of the albumen farinaceum and 

 ramosum. The walls are often thick and grown together, 

 so that the cells look as if they were cut out of a homogeneous 



