At ae eae ne 
66 MISSOURI BOTANICAL GARDEN. 
not to be distinguished (Pl. 55, fig. 7) as its hyphae pass 
imperceptibly over into those of the forming sheath. It 
ought to be said that hyphae of large as well as those 
of small diameter are found in the strands passing about 
the beech roots. The sheath grows rapidly along the root- 
let, until it reaches the point where that root joins a larger 
one. If another small root happens to be close by, the 
hyphae may grow over that one in similar manner, as evi- 
dently they did in several instances (Pl. 55, figs. 1 and 2). 
Shortly after being thus enveloped the rootlet begins to 
grow vigorously, at least it tries to. Lateral rootlets begin 
to appear close to the tip (Pl. 55, figs. 4 and 7 *b’), and 
they are pressed against the parent root by the enveloping 
sheath. In their endeavor to grow out, the roots execute 
circumnutating movements and gradually acquire the much 
contorted appearance already described. A number of 
stages in the process are shown in figs. 4, 5 and 6. Here 
the sheaths have been removed for clearness, and the 
branches have been pulled apart. Originally they were 
closely appressed. After some time the large skein is com- 
plete, and it is impossible to say how long the process 
would have continued. As each tubercle grew in size the 
enveloping hyphae kept pace with the growing roots. 
Sometimes two tubercles would touch, and then the hyphae 
of the two sheaths would fuse and thus bring about the 
appearance of a compound tubercle (Pl. 55, fig. 2). 
It now remains to inquire what the cause and meaning of 
the formation of these structures may be. The beech roots 
are as a rule covered by a fungus mycelium, which sur- 
rounds them and of which many hyphae enter the epider- 
mal cells. All observers, Frank,* Schlicht,t Sarauw,t 
* Frank, B. l.c. 
+ Schlicht, Alb. Uber neue Fiille von Symbiose der Pflanzenwurzeln 
mit Pilzen. (Ber. d. deutsch. bot. Gesell. 6: 269. 1888.) 
t Sarauw, G. F. L. Rodsymbiose og Mykorhizer saerlig hos Skov- 
traeerne. (Bot. Tidsskrift 18;127. 1893.) 
