345 
and its Mycorhiza . 
to conclude that the bladders are formed near the nucleus of 
the host-cell because it is at this point that the hypha is 
absorbing plastic substances most vigorously, and working 
them up into protoplasm more rapidly than they are conducted 
along the hypha. There is no indication of the wall of the 
hypha at this region being different in nature to the wall 
in the narrow portions of the hypha. (iv) Again, if the 
chemotropism of the hypha explains its growth in the 
direction of the nucleus, we may hope to find the same 
condition in other cases in which the Fungus is indubitably 
absorbing from the infected cell, i. e. in parasites. Rosen 1 
observed in the parasitic Puccinia asarina that the haustorium 
nearly always grew towards the nucleus of the attacked cell, 
and becoming closely applied to it caused deformations of 
the nucleus, and even pushed deep into it, driving in the 
nuclear membrane. Professor Marshall Ward informs me 
that in Hemileia (of the coffee-disease) 4 the haustoria often 
apply themselves to the nuclei of the host’s cells.’ The 
growth of the hypha towards the nucleus of the infected cell in 
mycorhiza , then, is not any evidence that the relation betwee7i 
Fungus and host is friendly and symbiotic , but is rather an 
indication that the hypha is absorbing food from the cell in 
which it lies. Still the apparent directive influence of the 
host’s nucleus has been observed in other symbiotic forms. 
Professor Marshall Ward tells me that in the leguminous 
tubercles he found the hyphae (?) growing toward the nuclei. 
Schlicht 2 * states that the mycorhizal hyphae in Paris quadri- 
folia often penetrate the nucleus. In Orchids it is easy to see 
that in mature cells the hyphae usually form a coiled 
mycelium around the nucleus, and Frank has pointed out 
that often the first trace of the mycelium is to be seen near 
the nucleus of the infected cell. 
Thus a hypha enters a cell because it is attracted thither 
by a chemotropically active substance, and goes towards the 
1 Rosen, Beitr. zur Kenntniss der Pflanzenzelle. Habil.-Schrift, 1892. 
2 Schlicht, Beitrag zur Kenntniss der Verbreitung und Bedeutung der Mycorhiza. 
Inaug. Diss. 1889. 
