286 COMPENDIUM OF GENERAL BOTANY. 



nicatioii on Tlie Adaptive Arrangements of the Storage -tissue of 

 Seeds. 



The chief function of the seed-coat is purely mechanical, 

 forming a protection against radial pressure. Seeds must be pro- 

 __^ tected against injury during their transport to the 

 places of germination ; they must also be protected 

 during their rest in the soil against the attacks of ani- 

 mals. Protection against evaporation usually goes 

 hand in hand with mechanical protection. The fact 

 that the formation of thick- nailed mechanically active 

 cells may take j)lace not only in the seed- or fruit- 

 coats, but also in the seed-albumen (endosperm), is 

 highly interesting. Much requires further investiga- 

 tion, l)ut we are enabled at present to arrange the 

 ^riphemlTmst ^■'^ll^™^^ "biological" groups of plants: 1. The 

 section of a seed-coat consiets of thin-walled cells and encloses the 

 endosperm of thick- walled albumen of the seedling : Colchicum^ 



Polygonatum Yigcu7n, Plantaoo, Arum. Rubiaceoi. 2. Thick- 



vulgare. ' ^ ' ' 



(After Haber- walled cclls of the sccd-coat and thin-walled endo- 

 sperm : Syringa^ Saxifragacecc-^ Ilellehorus, Papaver^ 

 Glaux, Hij^pojyhcB, Giaminew. (After Marloth.) (Compare 

 Figs. 91 and 109.) 



In still other cases both the seed-coat and the endosperm take 

 part in forming the mechanical tissue, PrrrzER ' made some very 

 interesting observations in regard to the adaptations for the germi- 

 nation of seeds with hard fruit-coats, as those of the Palmce. 

 Based upon his communication I will state that among the Boras- 

 sime the points for the escape of the seedling are preformed. The 

 thinnest part of the fruit-coat is immediately in front of the 

 embr^^o. In Cocos there is a valve at the point of germination 

 whicli is readily removed. This valve or opening corresjjonds in 

 position to the style. Pfitzer also found special arrangements for 

 holding the endosperm of the ripe fruit so that the seedling must 

 retain its proper position in regard to the germinal opening, as, for 

 example, conical projections from the seed-coat into the endosperm- 

 substance. 



On pp. 142, 143 we have explained more or less clearly that 



1 Ber. d. Deutscli. Bot. Ges., 1885, 



