Yami>OLSKY: Stiidy of OU paltn. 165 



We hâve seen from Figure 112, f^late XIII that iii an early stage of 

 germination the substances that are to be secreted as starch pass tlirough 

 tlie epidermal layer and thèse are laid down as starch grains ,in the inner 

 layers. The second layer contains smaller starch grains than the third 

 layer in which the starch grains are strikingly large. In such a stage the 

 présence or absence of starch grains indicates the activities of the cells. 

 The starch grains in that région show no corrosions. The starch at this 

 stage is stored in the cells. 



if vve examine the distribution of the starch grains in the whole embryo 

 at this stage (Figure 128, Plate XVI), we find that although starch is found 

 everywhere in the haustorium and in the embryo proper (not shown in 

 this figure) the densest zone is roughly between the outer layer and the 

 vascular bundles. This zone also coïncides with the zone of active cell 

 division. In the othei régions the starch grains are fewer. As one 

 approaches the embryo proper the starch grains show corroded areas. It 

 is to be remembered that in this stage most of the activities of the embryo 

 are in the région of the haustorium. In the other régions the activities are 

 very slight. More starch is being stored up than is being used. The condition 

 of the starch grain gives an index of the régional activity of the embryo. 



When the cotylédon has passed through the germ pore and the radicle 

 has burst through the sheath, digestion of the starch grains becomes more 

 pronounced judged from the condition of the starch grains. In later stages 

 when the meristem, under the epidermis has ceased to divide, storage and 

 translocation of starch are still active (Figure 141, Plate XVII). The présence 

 of starch grains in the epidermis of the haustorium where before no starch 

 grains appeared indicates a profound change in the physiological properties 

 of the cells. 



The micro-chemical tests employed for the détermination of the changes 

 of the oil, fats, and proteins hâve not been recorded in thèse observations. 



We hâve cited only a few of the physiological processes which the 

 endosperm and the haustorium register. Micro-chemical tests coupled with 

 thèse obvions microscopical and macrocopical indicators will présent an 

 even clearer picture of the physiology of the process. 



The haustorium in its structure, its bundles arranged in a ring the 

 character of its epidermis and its absorptive function, corresponds more closely 

 to the root than to any other organ of the plant. This is not said however 

 with the idea of defending the view that it is a modified root. 



Summary. 



1). The form of the haustorium dépends upon its position with référence 

 to the endosperm and also upon the form of the endosperm. 



2). The ultimate size of the haustorium dépends upom the size of the 

 endosperm. 



