FUXGI 



307 



eventually closed by the formation of a transverse wall in the protube- 

 rance. Cross-links, loops, «S:c., are frequently formed between branches 

 of the same hypha, or between originally distinct hyphae, by the resorp- 

 tion of the membranes at the point of contact. The coherence of the 

 ■compound thallus is most commonly effected by the more or less dense 

 interweaving of the hyphae, and by the cementing of them together in 

 many cases by an intercellular substance. The union of the component 

 hyphse may proceed so far, and the conditions of pressure, Ovic, be so 

 favourable, that a tissue 

 is formed resembling the 

 parenchyme of higher 

 plants. Being thus diffe- 

 rent from it in mode of 

 formation, the tissue in 

 question is icuTiedipseiido- 

 J)arenchyine. 



The form of hypha 

 described is not universal 

 among fungi. Sprouting^ 

 as it is called, is cha- 

 racteristic of the thallus 

 •of the yeast-fungus Sac- 

 charomvces, and it occurs 



in certain stages of other 

 fungi, such as Mucor. 

 This process consists in 

 the production of ovoid 

 or globular cells, by means 

 of excrescences which 

 remain connected by a 

 narrow base with the pa- 

 rent cell, and are eventu- 

 ally cut off at or before 

 maturity by a cross-parti- 

 tion. This process, on being repeated again and again undisturbed, 

 exhibits in the result the appearance of a copiously-branching hypha 

 formed of bead-like cells. This connection, however, is very easily 

 broken, and the usual appearance presented is that of small aggregates 

 of sprouting cells. 



Cell-co7itents. — The cells of fungi are characterised rather by the 

 absence of certain cell-contents than by the presence of peculiar sub- 

 .stances. The absence of chlorophyll and of starch-grains is most note- 



X 2 



Fig. 268. — Sacckarojityces cereinsicE Meyen. a, single cell 

 of beer-yeast ; b, c, stages of sprouting ; d, colony of sprout- 

 cells ; c, cell with four ascospores ; _/, one with two ; g, group 

 of ascospores with one sprouting ; h, further development of 

 a similar group (k x 750, the others much more). {e—k 

 after Reess.) 



