YampolsKY: Study of OU palm. 153 



lu ail thèse forms lie finds an agreemeiit in tlie rôle of the haustorium. 

 This organ grows at the expense of the eiidosperm. 



The periphery of the haustorium is coniposed of thiii-walled cells 2 

 to 4 tiines as long tiiey are vvide whose function it is to absorb the food 

 substances from the endosperm. The layer underneath is composed of 

 cells which are responsible for the continued growth of the haustorium. 

 The haustorium is supplied with two thick bundies which are continued 

 in the cotyledonary sheath. In contrast to the condition in ihe Grami/ieae, 

 the haustorium of the palm absorbs the crushed cell walls of the 

 endosperm. 



TSCHIRCH P) gives a long list of monocolyledenous plants that 

 possess an haustorium. For our purpose however, it seems unnecessary to 

 cite the many contributions that hâve been made on the subject of the 

 haustorium in plants. The few citations that hâve been given vvill serve 

 our purpose. 



The form of the haustorium. 



The form of the haustorium during its growth dépends upon its 

 position with référence to the endosperm. And the form of the entire 

 endosperm will ultimately affect the form of the haustorium. In a fruit 

 like the coconut the haustorium after it has passed out of the cavity in 

 which the embryo lies, into the large cavity of the endosperm, meets no 

 pressure and consequently develops equally in ail directions so that it is 

 usually bail shaped throughout its growth. Where the haustorium comes 

 in contact with a more résistant élément which it cannot readily digest it 

 conforms more or less to the shape of the obstruction. In the date seed 

 the haustorium ultimately comforms to the shape of the seed. 



TsCHiRCH p^) recognizes three types of haustoria found in the Mono- 

 cotyledons. 



Gramineae type — m this form the haustorium (scutelum) lies to the 

 side of the food storage tissue and it enlarges only slightly or not at ail 

 during germination. 



Palm type — in this form the haustorium is surrounded by endosperm 

 tissue and during germination grows into the endosperm growing and 

 enlarging at its expense. 



Zingiber type — in this form the haustorium although situated in tîie 

 center of the food storage tissue, does not enlarge appreciably. 



We hâve aiready called attention to the haustorium in the resting 

 embryo. In that stage it is sharply deliminated from the rest of the embryo 

 by a constriction. Furthermore in removing such embryos from the seed, 

 a color différence is seen, the haustorium is white, the rest of the embryo 

 is a very pale yellow with a faint tinge of green. In the resting state the 

 haustorium is cône shaped in appearance with a blunt apex (Figure 82, 

 Plate X). Parallel ridges run in the direction of its long axis. The ridges 



