1890.] Botany. : 369 
might name them so. Evidently the highly specialized requirements 
of pollen-tubes in the matter of nutrition are properly supplemented 
by highly specialized specific gonotropic irritabilities. The first is 
exactly paralleled by the specific nutrition requirements of the various 
parasitic fungi, which select each their own particular host-plant or 
animal, but the second is sus generis. 
When, however, the cells of zygophytic plants find their way to each 
other, as for example, the zodsphores of Pandosina, or the conjugating 
cells of Piplocephalus, there is scarcely a localisation of gonotropic 
irritability in one cell, and of gonotropie stimulation in the other, In 
such plants we are below the stage of specialization, and the whole act 
of conjugation is so unlike that of higher plants that a different name 
might properly enough be given to the peculiar directive influence 
which each conjugating cell has upon the other. They might truly be 
considered equally gonotropic and equally capable of stimulation ; but 
or the sake of differentiating between the bisexual movements and the 
unisexual, it might be well to term the movement shown by either of 
two similar conjugating gametes gamotropism. That gonotropic irrita- 
bility is a specialized type, an outgrowth from gamotrophic, goes with- 
out saying. Both are probably connected with the excretion of certain 
as yet unclassified chemical compounds, and the progression of the 
higher from the lower, with accompanying specializations, would o 
a field of research exceedingly interesting although exceedingly difficult. 
Carefully conducted and systematic experiments are needed along 
two lines, suggested in this brief note upon so fertile a subject: rst, 
Experiments to indicate the distance to which specific gonotropic 
stimuli can be propagated through the surrounding medium ; 2d, 
periments to show, by cross-pollenations, the relation between gono- 
tropic irritability and appropriate nutrition upon the growth and direc- 
tion of pollen-tubes.—Conway MacmiLian, Univ. of Minn. 
The So-Called Uredospores of Gymnosporangium.—Mr. 
H. M. Richards has carefully re-investigated the so-called uredospores 
of Gymnosporangium clavarieforme, and finds that Kienitz-Gerloff’s 
conclusions are erroneous. In a recent number of the Botanical 
Gazette Mr. Richards publishes the results of a series of germinations 
of both forms of spores, viz., the fusiform (teleutospores) and the 
clavate (the so-called uredospores), and shows that, however much they 
may differ in form, they certainly present no constant difference in 
their mode of germination. Under favorable conditions both give 
rise to the characteristic promycelium bearing sporidia. Under less 
Am. Nat.—March.—s. 
