MacDougaL- — Symbiotic Saprophytism . 4 1 
no important deviation from normal structure ; but those 
of endophytic habit exhibit such important modifications 
that it is sometimes difficult to establish their identity with 
hyphae outside the roots, a fact accounting for the small 
number of determinations of mycorhizal Fungi. These 
modifications consist in reductions in the size of the hyphae, 
the character and appearance of the wall, and in the forma- 
tion of organs or branches for reproduction or nutritive 
interchange. Bruchmann observed the formation of oospores 
on Pythium in the prothallia of Lycopodium (2), a fact confirmed 
by Janse, who also saw the ascospores of Celtidia in the 
roots of Celtis (16). Apart from these purely reproductive 
organs are others of similar origin which have perhaps 
become modified to serve vegetative functions. Among 
these are the ‘ sporangioles/ c vesicles/ and hyphal clumps 
found in or between the cells. The vesicles and sporangioles 
of various writers are short lateral branches of the hyphae 
which undergo a globular enlargement at the apex, with 
more or less variation as to content. These organs are 
notably large in the Orchidaceae ; and since they are generally, 
though not always, formed in the vicinity of the nuclei in 
the region of greatest metabolic activity of the higher 
symbiont, are to be regarded as organs for absorption 
and interchange. The occurrence of these structures between 
the host-cells would indicate the retention of the original 
function of reproduction. The hyphal clumps which have 
been noticed by the author in many of the mycorhizas 
described in this article, seem to be due to the repeated 
branching and chemotropic attraction of the apices of the 
branches toward a centre near the nucleus, without the 
formation of sporangioles. Several writers have noted that 
in some mycorhizas the sporangioles gave off numerous 
branches which became converted into the hyphal clumps, 
but in the material examined the intervention of the 
sporangioles could not be detected. 
The Fungus may be associated with prothallia, roots, or 
stems in the formation of mycorhiza. This union usually 
