490 THE SPECIFIC CONSTITUTION OF PROTOPLASM. 



the species of Cytisus developed flowers and fruits almost simultaneously under 

 the same external conditions, and it was noticed that the same real, if insignificant, 

 deviations were present in the external characteristics which had been present in 

 the parents. This different behaviour of plants which, on account of their form, 

 are described by the Botanist as distinct species, although closely allied, can indeed 

 only be explained by assuming that the protoplasm, though having on the whole a 

 similar constitution, is somewhat different in each species. 



As a further confirmation of the assumption that the protoplasm of each species- 

 possesses properties which are lacking in that of others, we may take the case of 

 the behaviour of pollen-cells in fertilization. If two kinds of pollen-cells are 

 brought to the stigmas of a plant, i.e. pollen-cells of two different species, it usually 

 happens that the one will fertilize the ovules with its pollen-tubes, while the other 

 will be without effect. And yet the conditions are the same in both cases, and the 

 difference in behaviour must therefore depend upon some difference in the proto- 

 plasm of the pollen-cells. Protoplasts which swim about as swarm-spores in the 

 same drop of water, exposed to exactly the same condition of light, heat, pressure, 

 &c., display a different behaviour if they belong to a different species. Those of 

 one species will always twist to the right, those of another always to the left, some 

 seek the light, others shun it for the darkest places. But since the protoplasm 

 behaves differently under the influence of the same ray of light, the same tempera- 

 ture, and the same pressure, the cause must be sought for in the tiny mass of proto- 

 plasm of which each swarm-spore is composed. 



The little amoebae which proceed from the spores of Myxomycetes are protoplasts 

 without a cell- wall; they live on dead parts of plants, where they feed, grow, divide, 

 and multiply. When the right time comes these amoebae fuse together to form a 

 body known as a plasmodium, which is ultimately converted into a mass of 

 sporangia (cf. vol. i. p. 572). Although the little amoebae of different species cannot 

 be distinguished from one another, and the plasmodia look like masses of formless 

 protoplasm which only differ sometimes in colour, the resultant sporangial forms 

 exhibit a remarkable variety ^ of forms. From the plasmodium of Stemonitis 

 fusca there arises a network of dark brown threads which is penetrated by and 

 borne on a central axis like the shaft of a feather (see figs. 355 l and 355 2 ); from 

 that of Spumaria alba is formed a white slimy mass resembling the " cuckoo-spit " 

 of the Cicadellidae and enveloping stem and leaves just in the same way (see fig. 355 3 ); 

 from the plasmodium of Dictydium cernuum there arises a globe-like lattice-work, 

 with strong longitudinal ribs and delicate cross-bars, which is carried on a hooked 

 stalk (see figs. 355 4 and 355 5 ); from the formless plasmodium of Craterium 

 minutum arise stalked cups of a gray colour (see figs. 355 6 and 355 7 ); from that 

 of Arcyria punicea short stalked conical bodies not unlike Strawberries (see figs. 

 3558, 9,10). the plasmodium of Lycogala epidendrum, which penetrates the wood 

 of dead tree-trunks, forms balls of the colour of red-lead, about a centimetre in 

 diameter (see fig. 355 n ), and out of the plasmodium of Leocarpus fragilis, which 

 spreads over dead branches and twigs, proceed stalked egg-shaped sporangia, with 



