Kusano, Further Studies on Aeginetia iudiea. 291 



securing as many chances to meet with a desired host-root, but 

 that as soon as one of the tendrils comes in contact with it the 

 seedling does not need the development of further tendrils. 



Usually only the apex of the tendril is responsive to the 

 Stimulus, but that the other portions may also react may be seen 

 in Fig. 11, where a tendril is shown twining around a root-hair 

 of a proper host-root (Zingiber). 



The tendril on Coming in contact with the host seems to be 

 retarded in growth as in the typical tendril (Pittin g, 1903, p. 604), 

 and it seems to wither and die away if kept indeflnitely away from 

 a proper host. 



In view of all these facts there can be any doubt that the 

 hair in Aeginetia- seedling is quite different both morphologically 

 and physiologically from the true root-hair, and that it most closely 

 resembles the typical tendril in its function. 



While the changes described above are taking place at the 

 radicular end, we can not find any notable change at the plumular 

 end except for a slight increase in size. The general form of the 

 embryo at this stage is then as reproduced in Fig. 12. It is 

 perhaps the last stage to which an embryo can develop without 

 Coming in contact with the host-root. Much starch-granules still 

 remain in the embryo and endosperm, and serve as the reserve 

 material for the further development of the seedling. 



Tubercle and Primary Haustorium. 



When a seedling as above described comes in contact with 

 a host-root by means of a hair-tendril further development follows 

 immediately. By a rapid multiplication of cells the seedling grows 

 so as to become visible to the naked eye. The newly produced 

 tissue gives rise. besides a primary haustorium, to a tubercle from 

 which the shoot and root-system of the plant are afterwards formed. 

 What is remarkable is that the multiplication of cells does not 

 take place unless the seedling becomes attached by one of the 

 tendrils to the host. Since the seedling is otherwise entirely in- 

 capable of further development in spite of the presence of the re- 

 serve material left in the endosperm, it follows that the further 

 development of the seedling is associated with the Stimulus of the host. 



The multiplication of cells occurs under the tendril-cells. The 

 parenchymatous tissue thus derived pushes and finally breaks the 

 latter, and comes to lie in direct contact with the tissue of the 

 host-plant. Until an organic connection becomes established between 

 the seedling and the host-tissue the multiplication of cells must 

 be due to the reserve material in the seed. The maximal size to 

 which the cell-mass can thus attain is less than 1 mm in diameter, 

 approximately the same as that to which the seedling of Orobanche 

 can reach with the help of its endosperm alone (Koch, 1883, p. 189). 



The cell-mass thus formed becomes a tubercle generally of 

 a spherical or oval form (Figs. 13, 14). It forms a large part of 

 the seedling, making the plumular end, globular cells and tendrils 



19* 



