200 The Botanical Gazette. [May, 
arrangement of members on a common axis, and their spiral 
sequence, by reference to definite mechanical causes. The 
mechanical basis for the theory of phyllotaxy was completed 
in Schwendener’s writings (1878), which showed that mechani- 
cal and geometrical conditions, especially the pressure ex- 
erted upon one another by the young members forming on 
the common axis, control the regularity of their positions in 
relation to each other. In the same way K. SCHUMANN 
(Custodian in the Botanical Museum at Berlin) is now at- 
tempting to explain the arrangement of floral organs. 
Closely akin to Braun's work, in that he established certain 
types, which, however, he considered to be phylogenetically 
the true starting points of later variations, W. EICHLER (Graz, 
Kiel, Berlin, died 1887) published in 1875 and 1878 the 
two volumes of his ‘‘Bliithendiagramme.” These are founded 
on general comparative investigations of the mature form, 
supplemented by a study of the development. From @ 
similar stand-point Pax (Custodian in the Botanical Garden 
at Berlin), wrote his ‘‘Handbuch der allgemeinen Morphologie 
der Pflanzen” which appeared in 1890. K. GOEBEL (Rostock, 
Marburg, Munich), on the other hand, tried in his ‘‘Entwickel- 
ungsgeschichte der Pflanzenorgane,” published in 1883, to be 
independent of the morphological ground-plans, to consider 
the distinct members of the body of the plant for themselves, 
and to be directed in their comparison only by the homologies. 
Development and comparative morphology are to him the most 
important aids in organography. 
Although the philosophical element in Braun’s most im- 
portant work, concerning rejuvenation in nature, published 
in 1851, is contrary to the principle of cause, which is now 
the basis of scientific thought, yet this work still holds atten- 
tion because of the freshness of its descriptions and the 
affectionate absorption of the author in his problem. For 
this reason the work contributed no slight stimulus to the 
further study of the lower cryptogams, especially of the 
Al Thuret performed certain experiments in 1853 which 
demonstrated the sexuality of the Fucaceg, but he attributed 
fertilization to the effects of the contact between spermatozoid 
and egg. Pringsheim was the first to show, in his researches 
published in 1855, that in generation ‘‘a mingling of the whole 
spermatozoid mass with the fructifying sphere takes place. 
Important works by Pringsheim, which made clear the whole 
