236 COMPENDIUM OF GENERAL BOTANY. 



nication on The 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- walled mechanically active 

 cells may take place not only in the seed- or fruit- 

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

 highly interesting. Much requires further investiga- 

 tion, but we are enabled at present to arrange the 

 " following " biological " groups of plants: 1. The 

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

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

 vui y a atUm Vi SGum , Plantago, Arum, Rubiacece. 2. Thick- 

 (After Haber- walled cells of the seed-coat and thin-walled endo- 

 sperm : Syringa, Saxifragacece, Helleborus, Papaver^ 

 Glaux, Ilippophce, Giaminecv. (After MARLOTH.) (Compare 

 Tigs. 91 and 169.) 



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

 part in forming the mechanical tissue. PFITZER ' 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- 

 ^since the points for the escape of the seedling are preformed. The 

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

 embryo. In Cocos there is a valve a.t the point of germination 

 which is readily removed. This valve or opening corresponds 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. Deutscb. Bot. Ges., 1885. 



