sect, i CRYPTOGAMS 341 



(p. 80), and contain numerous small nuclei dispersed throughout their 

 colourless protoplasm (Fig. 61, p. 60). In the cell contents are fre- 

 quently found flat globules and also glycogen, but never true starch. 

 Of all the Hyphomycetes the group of the Phycomycetes — the Water or 

 Algal Fungi — although occupying the lowest position, exhibit the 

 most evident connection with the Chlorophyceae. Their resemblance 

 to the Siphoneae, in particular, is especially pronounced, as their fila- 

 mentous, vegetative thallus consists of a single, simple, or profusely 

 branched multinuclear cell (e.g. Mucor, Fig. 269, p. 347). The thallus 

 of the higher Hyphomycetes is similarly formed of much-branched fila- 

 ments, but the filaments are septate, and so consist not of one 

 cell but of a row of cells. The filaments, whether septate or 

 unseptate, composing the thallus of the Fungi are termed hypHjE ; 

 the whole vegetative portion of the thallus formed by them, the 

 \ mycelium. The hyphse of a mycelium are, as a rule, either 

 /isolated or only loosely interwoven; they spread through the 

 substratum in all directions in their search for organic nourish- 

 ment. In many of the higher Fungi, however, the profusely and 

 irregularly branching hyphae become so inseparably knotted and 

 interwoven, that they seem to form compact masses of tissue. Where 

 the filaments in such cases are in intimate contact and divided into 

 short cells, an apparently parenchymatous tissue or pseudo-paren- 

 CHYMA is produced. Such compact masses of hyphal tissue are 

 formed by some species of Fungi when their mycelia, in passing 

 into a vegetative resting stage, become converted into Sclerotia, 

 tuberous or strand-like, firm, pseudo-parenchymatous bodies, which ger- 

 minate under certain conditions (Figs. 97, 98, p. 87). In the fruc- 

 tifications of the higher Fungi the hyphee are also nearly always 

 aggregated into a more or less compact tissue (Figs. 95, 96, p. 87). The 

 walls of adjacent cells or filaments of the mycelium are frequently 

 absorbed at their points of contact, and an open communication is 

 thus established between them. 



— Sexual reproduction is positively known to occur only in the 

 Phycomycetes or Algal Fungi. In this respect they approach on the 

 one hand the Conjugatae, on the other the oogamous Gonfervoideae and 

 Siphoneae, and have, accordingly, been divided into the two groups of 

 the Zygomycetes and Oomycetes. In both groups a complete reduction 

 of all sexual differentiation is sometimes manifested, while, in the 

 higher Fungi, the existence either of sexual organs or sexual repro- 

 duction has not been certainly proved; whereas in the green, inde- 

 pendently assimilating Algae exactly the reverse is true, and sexual 

 differentiation not only becomes more evident but the sexual organs 

 more complicated the more advanced the development. 



The formation of ASEXUAL spores is, on the contawy, of general 

 occurrence, and is effected in a great variety of ways. The produc- 

 tion in sporangia of large numbers of ciliate swarm-spores is only 



