CoxNixGHAM.—The Ustilagineae, or “ Smuts,” of New Zealand. 399 
as when a probasidium is produced which develops directly into an infection 
hypha, conidia being absent. In such a case the species is placed in one or 
other family on account of the possession of certain other characters. 
(See under “ Taxonomy.” 
In water the conidia produce short infection hyphae, seldom secondary 
conidia, but in nutrient solution they often give rise to secondary or 
din 
tertiary conidia by a process of budding. 
CYTOLOGY. 
The vegetative mycelium (prior to the formation of spores) is invariably 
binucleate until shortly after gelatinization of the walls of the sporogenous 
hyphae, when the two nuclei fuse, the mature spore being uninucleate. 
When the spore germinates the protoplasm passes into the probasidium, 
but the nucleus usually remains within the spore and there divides, the 
daughter nucleus passing into the probasidium. 
In Ustilago this probasidial nucleus and the one within the spore again 
divide, and all then migrate into the probasidium, where each takes up 
such a position that when the probasidium becomes septate each cell 
tains one nucleus. As each conidium is formed, one of the probasidial 
nuclei divides and the daughter nucleus migrates into the conidium. In 
those members of this family in which conidia are produced the conidia 
binucleate conidium germinates it produces an infection hypha, the cells 
1 division of the two nuclei. 
short conjugation-tube is | 
(or conidial tube), and the nucleus of the one migrates to the other. As 
in nutrient solution these conidia may produce an aerial mycelium from 
which secondary conidia arise, it follows that this mycelium, together with 
the mycelium becomes binucleate. Exceptions occur, however, -for 
Rawitscher (1912) has shown that with Ustilago Maydis Cda. (= U. Zeae 
Ung.) the conidia do not conjugate, the mycelium remaining uninucleate 
throughout its vegetative existence until the period of spore-formation, 
when during the formation of the sporiferous hyphae the ends of adjacent 
cells come in contact, their walls break down, and two nuclei come 
together in the swollen terminal region so These nuclei fuse 
almost immediately, so that the developing spores are uninucleate as in 
normal plants. 
This matter cannot here be discussed at greater length; further 
particulars may be obtained from the papers of Dangeard (1894), Harper 
(1899), Lutman (1911), Rawitscher (1914), Kniep (1921). 
