CH.V1II. MORPHOLOGY AND COURSE OF DEVELOPMENT. MYXOMYCETES. 431 



taneously into polyhedral portions with rounded corners, each of which encloses a ' 

 nucleus, and becoming invested with a firm membrane ripens into a spore. The spores 

 when first formed are somewhat larger, never smaller, than when they are mature. 



A comparatively small portion of the spore-plasm is expended in forming 

 the capillitium, a filamentous structure to be described more fully in section 

 CXXII, which spreads through the cavity of the sporangium and is connected 

 both with the wall of the sporangium and with the vesicles containing pigment 

 and calcium carbonate. The capillitium always appears before the spores, and 

 all the parts in the earliest state in which they have been examined are seen to 

 be formed and arranged exactly as when they are mature, only they are at first 

 extremely delicate and gradually acquire their subsequent firmness. These points 

 will be noticed again below. 



Fuligo, the ' flower of tan,' agrees with Physarum in all other points, but shows 

 a variation in the phenomena described above in the forming of the sporangia ; here 

 a number of plasmodia collect together from every side and become fused together 

 into a narrow dense reticulum with the shape of a cushion, which may come to be 

 twelve inches in breadth and one in thickness or may remain quite small. The 

 strands of this reticulum anastomose in every direction with one another. Then all 

 the spore-plasma passes after its separation into the inner portion of the reticulum 

 which swells proportionately, and then acquires the structure of the sporangia of 

 Physarum; the vesicles with calcium and colouring matter remain behind in the 

 peripheral layers, where they collapse and dry up forming a calcareous crust or rind 

 from one to several millimetres in thickness. 



Of the rest of the endosporous Myxomycetes, those, that is to say, which do not 

 belong to the Physareae, it may be confidently affirmed that the development of the 

 sporangia from the beginning of forming is thoroughly like that which has just been 

 described. The development of the spores is in all cases the same. Strasburger 

 succeeded in following the multiplication of the nuclei, which precedes the formation 

 of the spores, in Trichia fallax through all stages of the division, and ascertained their 

 morphological agreement with the divisions of the nucleus in many other vegetable 

 and animal cells. The case is the same also with the formation of the capillitium, 

 with some limitations naturally arising from generic differences. The elimination of 

 contained substances which leads to the formation of the spore-plasm is less copious 

 or there is none at all to be seen, as is the case in Stemonitis in all states 

 which have at present been examined, because the substances secreted in the 

 one case are wanting from the first in the other. The very first stages in the forming 

 of sporangia are in most instances imperfectly known because of the difficulty of 

 procuring plasmodia in the vegetating state. What is known of it in most genera 

 with simple sporangia, as Trichia, Arcyria, Dictydium, &c., corresponds with the fore- 

 going description of the Physareae. On the other hand the large and often thick- 

 walled spore-receptacles of Lycogala, Reticularia, Lindbladia and others are formed 

 by such an accumulation and intermingling of numerous plasmodia as has been 

 described in the case of Fuligo. Rostafinski applies the collective name aethalium to 

 all bodies which originate in these combinations of plasmodia. Little more is known 

 of the processes of differentiation in their development than can be concluded from 

 the mature state. 



