i8 Sforc-foniiai'ioii. 



protoplasm. At the same time, the hypha? give rise at various points to in- 

 wardly curved branches, and several of these branched spore-forming hyphae 

 lay themselves together and twist themselves into a small ball, not unlike 

 what happens in the formation of a lichen-thallus. These convoluted and con- 

 torted hyphfe, being gelatinous, soon become so intertwined and entangled 

 that they lose their individuality, and on the exterior of this gelatinous ball 

 other hyphse are seen encircling it. These hyphae are also gelatinous and 

 soon become indistinct, although sometimes there are traces of a concentric 

 arrangement. Spore-formation is confined to the central gelatinous ball in 

 the middle of which it commences as circumscribed clear spots, which soon 

 assume a distinct outline, become brownish in colour, and are diSerentiated 

 into spore-like bodies varying in number from four to sixteen, or even more. 

 These bodies again subdivide, so that when the spores arrive at maturity 

 there are sixty to a hundred, or even more of them, in a spore ball. In the 

 young state these developing spores are polygonal from mutual pressure, and 

 they are to be found in spore-balls not more than 50 // in diameter. In the 

 subsequent development of the spores, the ball increases in size and the gela- 

 tinous zone swells also, but when the spores assume their characteristic deep 

 brown colour, this gelatinous zone begins to be absorbed, having been utilized 

 in the development of the spores. In spore-balls of 70 /< in diameter, the 

 gelatinous zone is only from 4 to 6 /i thick, and there is no trace of it in the 

 fully matured spore-balls, except occasionally as in &. solidum, where the rem- 

 nants were at hrst regarded as sterile cells like those in CJrocystis. 



In a section of the affected portion of the host-plant concentric layers of 

 spore-balls to the number of six to eight occur, the peripheral layer being the 

 oldest, having been pushed outwards by the continued formation of the young 

 spore-balls in the centre. 



Thecaphora and Tolyposporium. 



The development of the spores has not been completely traced in these 

 genera. The spore-bearing hyphae are intertwined and interlaced into a 

 dense mass, and the early stages of the spore-balls are difficult to determine. 



TiLLKTIA. 



The formation of spores in this genus has been investigated by several, but 

 it is to Fischer von Waldheim that we owe the most complete account of the 

 process which is as follows : — When spores are about to be formed, the spore - 

 bearing hyphse give off pear-shaped buds in succession from their sides. 

 (Plate I., cj). These outgrowths increase in length, and at the same time the 

 swollen end of each increases in diameter and becomes rounded, so that it is 

 ultimately attached to the hyphse by a thin stalk (Plate I., h). The contents 

 derived from the hyphse are granular and vacuolated and particularly rich 

 in oil, and the membrane becomes somewhat gelatinized. Just before reaching 

 maturity the gelatinized membrane is absorbed and the young spore acquires 

 a double contour, the epispore gradually becoming darker and uneven 

 (Plate I., i, j). In some cases the gelatinous membrane of the hyphse invests 

 the spores up till the time of ripening, and then disappears without leaving any 

 trace. The stalks or connecting branches soon wither, and to many ripe spores 

 their remains continue attached (Plate I., k). 



While in Ustilago the spore-bearing hyphse directly break up and form 

 the spores, in Tilletia the spores are formed singly at the ends of branches. 



Entyloma. 



De BaryS has investigated and described the development of the spores, 

 and it is found to be very similar to that of Tilletia. The fertile mycelium 



