258 The Botanical Gazette. 
and in addition those carried on by Atwater, !9! Bréal,1! 
Bertholet,'°* and Vines,!°* conviction becomes inevitable 
that leguminous plants can only develop tubercles when ex — 
cited by the presence of certain micro-organisms. 
The important question then is, can these various conflict 
ing notions of the biology of the microsymbiont be harmon _ 
ized? Leaving out of consideration for the present the real — 
nature of the organism it will be admitted by those whotake — 
the trouble to familiarize themselves with the scope of the 
work covered by the most important investigations thattheor — 
ganism in question consists of an elongated thread-like struc 
ture, which branches freely within the tubercle and possesses 
enlarged portions which present a more or less finely lobed sur- 
face; and very much smaller forms which must exist to some 
extent within the tubercle, are capable of multiplying ine 2 
tificial media, and, when transplanted from artificial media to 
the roots of lezuminous plants, are capable, under these a 2 
natural conditions and the stimulus of the macrosymbiont, @ — 
growing out again into the thread-like structures. 
Beyerinck!°® then probably overlooked the rea 
trations and descriptions it seems reasonably certain that, 12 
some instances at least, he was dealing with the true orga 
ism in his artificial cultures. An examination of his figue | 
C shows the organism to be very simila 
my own cultures represented in figures II and 12, 
ark ge 
says: ‘Die Colonien auf Gelatine bestehen aus staee 
buckelten bacteroidenihnlichen Stibchen.” | The — 
this one was obtained from tubercles of Vicia hirsuta. 
Recently Nobbe, Schmid, Hiltner and pote 
considering the organisms to be bacteria, admit 
*°1Atmospheric nitrogen as plant food. Bull. no. 5 
*°?Fixation de l’azote par les légumineuses. 
l’Acad. d. Sciences, Paris. crx. Oct. 28. 1889. certain terres 
103Experiénces nouvelles sur la fixation de l’azote pat xvi. Avril, 
et par certaines plantes. Ann. d. Chim. et d. Phys. VI. the roots of b 
_ 1°4On the relation between the formation of tubercles Gotaty n(t 
_— and the presence of nitrogen in the soil. Anz. 
390-3 
1°3Bot. Zeit. 1888. ; Leguminoses. 
1°6Versuche iiber die Stickstoff-Assimilation der 
Versuchs-Stationen, xxxrx (1891). 
| nature of s 
the thread-like structures. From a careful study of his illus- 
; in 
r in form to those 
plate a, 
ae he 
and to those obtained by Laurent. In describing epee 
106 while 
hat in the 
Storrs’ School AF 
Exp. Station, Conn. Oct. 18809. Compt Rend. herbd. 4. SH # 
