598 
Journal of Agricultural Research 
Voi. xxvi, na. i» 
In Mindum, also, the host nucleus moves to the haustorium but does not 
become its sheath, for the nucleus can be seen alongside of the haustorium 
long after the sheath is fully formed. 
Smith (34) , also studying Erysipheae, concludes that— 
the host nuclei and the haustoria are indifferent to each other. 
He notes that as the haustorium penetrates the outer wall of the epi¬ 
dermal cell the host secretes cellulose, forming a layer surrounding the 
growing haustorium. The heavy sheath of the haustorium in that case 
consists of cellulose secreted by the cytoplasm of the host cell and 
partially disintegrated by secretions of the fungus. Of course it is not 
impossible that some cellulose is secreted about the haustorium in Min- 
dum, but it is doubtful whether the sheath as a whole could have such an 
origin, for cytoplasm about the haustorium is killed quickly. It is pos¬ 
sible that an originally thin cellulose sheath later becomes partially 
disintregrated and enormously swollen, like the outer walls of some of 
these cells. 
The motion of living protoplasm toward the haustorium, as it occurs in 
Mindum, is by no means unique. Eriksson ( 11 ), in his studies of Puccinia 
graminis Pers. on oats, figures the nucleus and haustorium uniformly in 
contact with each other (pt. IV, PI. 2). This contiguity plays a part in 
his theory of “Mycoplasm.” Rosen (, 32 ), in his study of Puccinia asa- 
rina Kunze on Asarum, noted that the haustorium is close to the host 
nucleus and often wrapped around it. He interpreted this to mean that 
the haustorium grows to the nucleus rather than the reverse. Blackman 
and Welsford (7), in studies of infection by Botrytis cinerea Pers., state: 
As the hyphae penetrate through the epidermis, the cells of the palisade parenchyma 
become affected. First the nuclei move upwards towards the epidermis, then gradu¬ 
ally they begin to disintegrate ... 
They did not feel certain, however, that this nuclear movement was a 
response to the fungus. Dey ( 10 , p. 310 ), working on Colletotrichum 
lindemuthianum (Sacc. and Magn.) Scribner, says: 
When the infection hypha enters the cavity of the cell, the protoplasmic contents of 
the latter apparently flow toward the hypha and collect around it. Movement of nuclei 
similar to that found by Blackman and Welsford in the bean cell invaded by Botrytis 
cinerea , has never been observed in this case. 
Boyle, studying infection by Sclerotinia libertiana Fuckel (<?), says: 
Meanwhile the nuclei of the palisade cells beneath the point of attack move toward 
the top of the cells . . . 
An interesting side light is shed on this motion of living protoplasm 
toward the source of trouble by a comparison with the older work on 
chemotaxis and traumataxis of the nucleus. Ritter (31 ), working with 
the living epidermis of onion bulb scales, found that in response to a 
wound the nucleus and part of the cytoplasm of near-by cells flow to the 
side of the cell nearest to the wound. He believed that the nucleus was 
passive, being carried by the flowing cytoplasm. This reaction, known 
as traumataxis, is seen first in the cells nearest the wound, later in cells 
farther and farther away. The reaction weakens with distance. Later 
there is recovery, first near the wound and later in the more distant 
regions. Burning produces the same effect as pricking or cutting. Plas- 
molysis with sugar solution before wounding does not inhibit the reaction* 
Chemicals produce a reaction (chemotaxis) similar in all respects but 
slower. Positive chemotaxis was observed in response to a great variety 
