July 1, 1899.] 



KNOWLEDGE 



161 



THE MYCETOZOA, AND SOME QUESTIONS 

 WHICH THEY SUGGEST.-IV. 



By the Right Hon. Sir Edward Fry, d.c.l., ll.d., f.r.s., 

 and Agnes Fry. 



CAPILLITIUM. — It is impossible to consider the form 

 of the sporangium without reference to the capilli- 

 tium, !.('., the system of hairs contained within it, 

 and sometimes entering into union with it as part 

 of its structure. This capillitium is often of great 

 beauty. It is formed before the spores in the course of 

 development, and it is probable that it performs a part in 

 the dispersal of the spores. Sometimes, as in Trithia 

 (Fig. 12), the hairs lie free amongst the spores. In this 







>s^ 



Fig. 12. — Elaters and spores of Trichia varia. 



genus the hairs are furnished with spiral thickenings, 

 which give them very much the appearance of a twisted 

 cord, and they are hygroscopic, i.e., under the influence of 

 moisture they twist and twirl and thus separate and dis- 

 perse the spores. In Trichia the sporangium opens by the 

 bursting of the upper part of the case, and then the hairs, 

 covered with the spores, pour out over the remaining part 

 of the sporangium, so that it appears as if covered by a 

 piece of delicate fur. 



In some cases the hairs have not only a spiral thicken- 

 ing, but are furnished with projections, bristles or cogs of 

 varying shapes. In one species, Hemitriclna rubiformis, 

 the hair is so thickly beset with bristles that under the 

 microscope it looks like the prickly stem of the bramble, 

 and hence it derives its specific name. In some genera 

 the hairs, as well as the spores, are remarkable for their 

 bright golden yellow colour. 



A connected system is presented by the capillitium of the 

 beautiful genus Arcyria (Fig. 6). The immature sporan- 

 gium is a long egg-shaped case standing on a pedicel ; as 

 it ripens the upper half or two-thirds of the membrane 

 burst and fall off, leaving the lower part to form a cup (c), 

 from which is seen to arise a thick web of fibres, almost 

 like a pillow made of delicate horsehair (cap). These fibres 

 are elastic, and so soon as the wall of the upper part of 

 the sporangium gives way they expand to a height and 

 breadth greatly in excess of the capsule in which they were 

 contained. There can be little doubt but that these elastic 

 fibres when mature must exert a great upward and outward 

 pressure on the walls of the sporangium, and no doubt 

 they hasten the disappearance of the upper parts of the wall. 



Ln some species the system of hairs remains attached to the 

 cup, which is the abiding part of the sporangium wall ; in 

 other species it is attached to the interior of the stalk only by 

 a few branches, and then it is apt to fall away from its cup. 



The likeness between the hairs of the sporangia of the 



genera Trichia and Hemitrichia , and of the Jungermanni^ 

 is very close, and the same variety of arrangement is found 

 in both cases. Both families exhibit elaters marked by 

 spiral thickenings {see Fig. 12) ; but in the myxies these 

 thickenings appear to be external, whilst in the Junger- 

 mannife they are generally, or always, internal. Both 

 groups show differences in the number of these spiral 

 thickenings ; they are sometimes single (as in Hemitrichia 

 Wiijandii), or double, and sometimes reach to as many as 

 six (in Hemitrichia clavata). In both groups the hairs are 

 sometimes free and lie loose amongst the spores, and, Ln 

 other cases, are joined together into a system — a regular 

 capillitium, attached to the base of the sporangium. The 

 ■ hingermanniit epiphylla is a good illustration of such a 

 regular system of hairs. In both groups the hairs or elaters 

 appear to perform the same duties, of assisting by a pressure 

 from within in forcing the sporangia open and of dispersing 

 the spores by means of their hygroscopic activities. 



In some sporangia, the most marked feature is a 

 columella — i.e., a prolongation of the pedicel, usually forming 

 a column or a central line through the sporangium, but 

 sometimes hemispherical and globose. In some genera it 

 extends for only part of the height of the sporangium ; 

 sometimes for its entire height. A portion of such 

 columella is seen in Fig. 13. To the columella the system 

 of hairs is attached in many divers forms and ways. In 

 Lamproderina the column reaches part of the way up the 

 sporangium, and from near its summit it gives off a great 

 mass of hairs spreading in every direction, so as to form a 

 globe of anastomosing hairs. In Enerthenemn the column 

 is carried to the top of the sporangium, and spreads into a 

 sort of capital, the top of which is part of the surface of the 

 sporangium, and here theglobe of slightly branching hairs is 

 attached to the top, and falls down and fills the sporangium. 



More complicated and more beautiful forms arise when 

 the hairs branch out from all along the columella, and 

 anastomose with one another so as to form a perfect 

 network. In these cases the whole of the walls of the 

 sporangium is supported by the ends of the hairs, and is 

 usually very fugacious, and soon falls off, leaving a tree- 

 like structure oi delicate branches. The genua Comatric/ia 



FlO. 13. — Capillitium of Stemoaitis fusca. 



shows round or ovoid heads, not unlike the system of 

 branches of an oak (see Fig. 11). The genus Stemonitis 

 has taller tree-like growths, which often remind one forcibly 

 of a Lombardy poplar. Fig. 7 shows a group of sporangia. 

 Fig. 13 shows a portion of the capillitium when the spores 

 have been shaken out. 



