THE ENDOSPERM 179 



ing intercellular spaces. A similar extensive growth and 

 escape of the endosperm is reported to occur during the germi- 

 nation of the seeds of Ricinus. In the germination of the seeds 

 of certain Piperaceae (Peperomia and HecJceria) Johnson 53 ' ss 

 has described the endosperm as bursting out of the seed-coat, 

 and continuing to jacket the embryo, which at germination is a 

 globular undifferentiated mass of cells, until the root, hypocotyl, 

 and cotyledons are organized. In the same papers Johnson calls 

 attention to the fact that the endosperm of these Piperaceae 

 is not a storage region, but digests, absorbs, and passes on food 

 material to the embryo from the much more abundant peri- 

 sperm, which is the real storage tissue. This restriction of the 

 function of the endosperm Johnson S4 had already pointed out 

 in Saururus, and suggests the probability that this same relation 

 hetween endosperm and perisperm obtains in all seeds with 

 abundant perisperm as in Polygonaceae, Chenopodiaceae, Phy- 

 tolaccaeeae, Caryophyllaceae, etc. The following quotation 55 

 will serve to make plain the author's point of view: 



" Observations thus far made lead me to believe that in the peri- 

 sperm-containing' seeds mentioned the embryo sporophyte of the second 

 generation is never nourished by the parent sporophyte directly, but 

 always through the intermediate gametophyte. In general, then, we 

 find that the food substance supplied to the embryo by the nucellus 

 may pass through the endosperm and be stored in the embryo during 

 the ripening of the seed, as in Cucurbita and Phaseolus ; or, secondly, 

 the food may be stopped in transit between the nucellus and the embryo 

 and stored in the endosperm, there to be held during the resting period 

 of the seed and delivered over to the embryo only at the time of sprout- 

 ing, as in Ricinus, Zea, and apparently all Gymnosperms ; or, finally, 

 the food supply for the developing embryo may be stored in the nucel- 

 lus itself until the time of germination, when it is passed on to the 

 embryo through the endosperm, as in Saururus, Peperomia, Phyto- 

 lacca, Carina, and others." 



The phenomenon of xenia has a direct bearing upon any 

 discussion of the endosperm. The name was applied by Focke, 5 

 in 1881, to the direct effect of pollen on seeds and fruits out- 

 side of the embryo, as shown in hybrids. The case of peas has 

 long been cited, but Giltay 14 has shown that the effects referred 

 to occur in the cotyledons, and therefore can not be considered 

 as xenia. So far as definitely known, the effect of foreign 

 pollen outside of the embryo is observed only in the endosperm, 



