2<> Stopea and Fujii, The nutritive relationa of the Borroonding tissues etc. 



take i" be the natural resull <>f their lesser |>hysiologicnl importance 

 in this group. Because, aa we stated above the amount of deposited 

 Eood Sintis in the endosperm previous to the Formation of the embryo 

 is -mall in Pinus, so thal what the egg requires is already to band 

 in soluble forma in the surrounding cells, and the jackel cells have 

 not gol to be so active in preparing stored food for it; also the 

 embryo is so eariy carried down through the jacket cells into the 

 endosperm by the suspensors that the jackel cells can do but little 

 for it in comparison with what the jacket cells can do for the 

 proembryo of Ginkgo for example. In many of the higher 

 Grymnosperms, the differentiation of the jacket cells is not very 

 great and thej may be but short lived, while in some cases they 

 are hardlv recognisable as specially differentiated from the 

 surrounding endosperm cells. For example in Thuja as descrihed 

 by Land 1 ) the jacket cells, which do not seera to be so 

 much differentiated as in Pinta appeär at the tinie of cutting 

 off of the neck cells, and break down shortly after fertilization. 

 Xnw in Thuja we found that so little solid food is deposited 

 in the endosperm that even after the embryo has reached a 

 considerable size the quantity of starch in the surrounding cells is 

 very trifling. 



In Land's' 2 ) account of Ephedra he describes in the 

 gametophyte a basal "storage" region, and an upper archegonial 

 region in which all the cells are very feebly organised and the 

 jacket cell walls "never at any time thick, become so tenuous that 

 they can scarcely be seen and evidently öfter little resistance to 

 the passage of food into the central cell"; these cells break down 

 altogether at the time of fertilization. According to our view their 

 lack of differentiation is correlated with the fact that the storage 

 region is distant from the egg cell and they have therefore no 

 immediate service. 



\\ r e have not as yet had the opportunity of examining all the 

 genera of Gymnosperms from this point of view so that it is quite 

 possible that exceptions may exist and a well differentiated jacket 

 layer be present even when there is no deposition of food near the 

 egg; but in such a case there may he some other physiological 

 significance for these cells. 



Up to the present all the workers have laid much stress on 

 the nuclei and nucleoli of the jacket cells alone as the direct source 

 of nutrition of the egg cell. The facts now brought forward shew 

 this view to be untenable. Every cell of the endosperm does its 

 share of temporaryily storing and passing on the food to the egg, 

 thougb apparently the jacket layer is specially active and it is 

 possible that the nuclei of the jacket cells may play some important 

 part in the working up of the soluble simpler Compounds into 



!) La ml. W. J. G., ,.A morph. study of Thuja". (Bot. Gaz. Vol. XXXIV. 

 1902. p. 249—258.) 



-) Land, \V. J. G., „Spermatog. aud oogen. in Ephedra trifurca". (Bot. 

 Gaz. Vol. XXXVLLI. 1904. p. 1—16.) 



