PCa ga! me een Che eet ey, Pees Re ee MT 
rec. oF tet" 
PS 
ay ONS 
A SCLEROTIOID DISEASE OF BEECH ROOTS. 65 
to the tip (‘e’). The meristem cells are very large, 
compared with those found in the roots of the myco- 
rhiza. 
In tracing the development of these tubercles the struc- 
ture of the beech roots as they are found normally must 
be remembered. Since the researches of Frank * it is 
generally recognized that the roots of the beech when 
grown in humus soil, are surrounded at their tips by a 
mantle of fungus threads, which grow in more or less 
intimate contact with the root itself, and, according to 
Frank, sustain a sort of symbiotic relationship, known col- 
lectively as the mycorhiza. But few of the fungi to which 
these hyphae are supposed to belong are known as yet, but 
wherever beeches occur in humus soils, some fungus is 
found associated with their roots. 
This is true of our American beech, Fagus ferruginea, 
of which roots from different localities have been fre- 
quently examined. The roots of the mycorhiza are as a 
rule coralloid in form, i. e. short, frequently branching, 
grayish-white in color, but never, so far as I have seen 
them, contorted or hypertrophied in any way. 
The trees at Grand View had no fungus mantle on the 
ultimate root tips of the larger roots on which tubercles 
were found. All rootlets free from the tubercles were 
short, with a blackened epidermis. All stages from such 
short uncovered roots to the full-sized tubercle were seen, 
and the method of growth appears to be as follows. The 
strands of some humus inhabiting fungus happen to grow 
over one of the ultimate branches of the beech root. For 
some reason the hyphae of that strand then develop pro- 
fusely at the point of contact and gradually grow around 
the root. The beginning and end of the strand are soon 
* Frank, B. Uber die auf Wurzelsymbiose beruhende Ernihrung 
gewisser Baume durch unterirdische Pilze. (Ber. d. deutsch. bot. Gesell. 
$:128. 1885.)—Uber die physiologische Bedeutung der Mycorhiza. 
(Ber. d. deutsch. bot. Gesell. 6; 248. 1888.) 
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