SECT. I 



CRYPTOGAMS 



343 



turn coalesce. At the period of spore-formation the plasmodium 

 creeps out from the substratum towards the light and air, and, after 

 coming to i-est, is converted into a single or into numerous and closely 

 contiguous fructifications, according to the genus. On the periphery 

 of each fructification an outer envelope or peridium is formed ; while 

 internally the contents of the fructification separate into spores, each 

 of which is provided with a nucleus, and enclosed by an outer wall. 

 In many genera, part of the 



Fig. 255. — Ripe fructifications, after discharge of the 

 spores. A, Stemonitis fusca (x 10); B, Arcyria 

 punicea(x 12); C, Crihraria rufa{x 32). 



internal protoplasm within the 

 SPORANGiuiM or spore-receptacle 

 is utilised in the formation of 

 a CAPiLLiTiUM (Fig. 255, 5;, 

 consisting of isolated or reticu- %t 

 lately united threads or tubes. ^-^ 

 Upon the maturity of the 

 spores, tlie peridium of the 

 sporangium becomes ruptured, 

 the capillitium expands (Fig. 

 255, i>), and the spores are dis- 

 persed by the wind, aided by 

 the hygroscopic movements of 

 the capillitium. In the case 

 of the genus Ceratiomyxa, the process is somewhat simplified, as the 

 fructification is not enveloped by a peridium, and the spores are 

 produced at the extremities of short stalks. 



The germination of the .spores (cf. Fig. 58, Chondrioderma) takes place in water 

 or on a wet substratum. The spore-wall is ruptured and left empty by the escaping 

 protoplast. After developing a flagellum or cilium as an organ of motion, the 

 protoplast swims about in the water, being converted into a swarm-spoke (Fig. 58, 

 e-g) which resembles a Flagellate, with a cell-nucleus in its anterior or ciliated end, 

 and a contractile vacuole in the posterior end of its body. Even within the spore 

 a division may take place, so that two swarm-spores are liberated. In some 

 species the swarm-spores can increase in number by fission. Eventually the 

 cilium is drawn in, and the swarm-spore becomes transformed into a jiyxamoeba ; 

 these have the capacity of multiplication by division. In conditions unfavourable 

 for their development they surround themselves Mith walls, and as microcysts 

 pass into a state of rest, from which, under favourable conditions, they again emerge 

 as swarm - spores. Ultimately a number of the myxamcebae approach close 

 together (Fig. 58, I) and coalesce, forming small plasmodia (Fig. 58, ni), which in 

 turn fuse with others into larger plasmodia, but no fusion of nuclei is associated 

 with this. The amoebae and plasmodia feed upon nutritive particles which they 

 absorb, and exhibit active streaming movements of the protoplasm. After some 

 days the plasmodium becomes converted into the fructification. 



According to the investigations of Jahn and Keanzmn (^2) a conjugation in 

 pairs of the nuclei (kaygogamy) takes place in the young sporangia, and the un- 

 paired nuclei degenerate. This nuclear fusion can be regarded as a sexual process. 

 The diploid nuclei, shortly befoi ; the delimitation of the spores, undergo a hetero- 

 typic division in which the number of chromosomes is reduced to the half number. 



