176 DIVISION II.—COURSE OF DEVELOPMENT OF FUNGI. 
the sporogenous hypha, in place of which a group of 2-4 delicate cells subsequently 
makes its appearance after some intermediate stages which have not been clearly 
ascertained; these cells are firmly united together and develope into spores, and 
the group in its early stages has slender curved hyphal branches growing close 
round it and forming an envelope for it. The hyphae of the envelope are divided 
by transverse walls into short cells, most of which disappear as the spores ripen, 
while a small number of cells varying with the individual develope into persistent half 
lenticular envelope-cells, which lie close upon the group of spores as it matures. 
The envelope appears to be formed at earlier or later periods in the development 
according to the species, and the division of the spore-primordia to be sometimes 
omitted, as only one ripe spore is not unfrequently found inside a group of envelope- 
cells. According to Prillieux the process is much more simple; a number of 
sporogenous hyphal branches become felted into a knot, and one or more branches 
form a spore acrogenously, as in Tilletia, while the cells of the other branches 
develope more or less perfectly into an envelope; but the envelope may be omitted 
and then the spore is formed as in Tilletia. My older observations agreed pretty 
well with these statements of Prillieux, but it would be desirable to have other 
confirmation of them. 
The commencement of a spore-cluster in Sorosporium and Tuburcinia, ac- 
cording to Woronin, is also a short turgid lateral branch, sometimes perhaps two 
branches, lying close upon one another. Every such primordium is then wrapped 
up in a tangle of the many ramifications of slender hyphal branchlets, which become 
woven together into a round compact coil. No further differentiation is at first 
perceptible in the coil. When it has grown to a certain size its central portion 
consists of a compact group of delicate polyhedric cells, which then ripen all 
together into perfect spores without further perceptible division by multiplication. 
The group is at first still enclosed in a dense many-layered web of hyphae, but this 
disappears as the spores mature, in Sorosporium with a previous conversion into 
mucilage. The first formation of the group of spores in the coil is not clearly 
ascertained. Frank’s statement, that each spore comes from a turgid cell of one 
of the original filaments of the coil, and that the other parts then form the temporary 
envelope, is plausible but requires more distinct proof. We learn from Fischer 
von Waldheim that spores sometimes occur even in Sorosporium Saponariae, which 
are abjointed singly and without envelope on the extremity of a hypha as in Tilletia. 
If these spores really belong to Sorosporium, as they must be supposed to do without 
proof to the contrary, and not to a parasite of the plant, Frank’s view finds in them 
material support. 
The development of the spores has not been closely followed in the genera 
Thecaphora and Schizonella, Schröt., which certainly come near to Sorosporium. 
Section LVI. The single ripe spore of the Ustilagineae is usually round or 
polyhedric and has the ordinary structure of firm Fungus-spores,—a delicate colourless 
endosporium enclosing the protoplasm, and a stout episporium, which in most species, 
and also in a form of Entyloma distinguished as Melanotaenium, is dark-coloured, 
and in many has a delicacy of structure and superficial marking which is character- 
istic and useful for the discrimination of species; in some cases it has a distinct 
germ-pore. It is only in the majority of the Entylomeae that the thick stratified 
