270 BOTANICAL GAZETTE [APRIL 
intercellular spaces, since they become larger the further they 
occur from the region of origin. 
In the early stages of the growth of the tubercles, before 
they contain the algae, numerous lenticular areas may be 
observed at their bases and also upon the adjacent part of the 
root which bears them. These peculiar areas have openings in 
them which appear as crevices, and as the tubercles grow older 
the whole area frequently breaks away, and it is doubtless 
through these rents that the algae effect an entrance. Together 
with the algae the fungi and bacteria also enter, the latter forms 
penetrating the cells and causing the enlargement of the inter- 
cellular spaces. 
In reference to the symbiotic relations which exist between 
these various organisms it is difficult to speak with any cer- 
tainty. The fungi and bacteria doubtless find congenial condi- 
tions of moisture and food in connection with the algae, and are 
in turn the principal agents in producing the intercellular spaces 
in which the algae thrive. It is barely possible that there may 
be some such chemical attraction between the fungi and algae and 
the cells of the differentiated layer as has been stated by Miyoshi. 
It has been demonstrated by Vines,° Frank,? MacDougal,’ 
and others that fungi growing upon the surfaces of cells or 
within them may aid in nutritive work by converting free nitro- 
gen and the simpler nitrogen compounds into the more complex 
forms used by the plant. The same function has been attributed 
to certain algae by Prantl,9 especially including the nostoc 
forms. This last observation suggests the possibility of the use 
5 Ueber Chemotropismus der Pilze. Bot. Zeit. 52 : 1-28. p/. 7. 1894. 
§On the relation of the formation of tubercles on the roots of Leguminosae and 
the presence of nitrogen in the soil. Ann. Bot. 2: 386- 389. 8. 
7 Ueber die auf Wurzelsymbiose beruhende Ernahrung gewisser Baume durch 
unterirdische Pilze. Ber. deut. bot. Gesell. 3 : 128-145. f/. zo. 188 
8 Symbiotic saprophytism. Ann. Bot. 13: 1-47. pls. 7, 2. 1899. 
9 Die Assimilation freien Stickstoffes und der Parasitismus von Nostoc. Hed- 
wigia 28: 135. 1889. 

