116 



KNOWLEDGE, 



[Mat 1, 1899. 



We propose hereafter to consider somewhat more in 

 detail the peculiarities of these two sets of aberrant forms ; 

 but they will be better appreciated after we have dealt with 

 the larger group. We therefore now turn to the myxies 

 which carry their spores within the sporangium, and we 

 shaU indicate some of the points of structure of which 

 use has been made for the purposes of classification. 



Frtjctificatiox. — Perhaps the point of distinction which 

 first arrests the eye of the student is the variety of form in 

 which these organisms fructify and bear their spores. 



These forms, to which different designations have been 

 given, may be considered : — 



a. The sporangium, a term which is sometimes applied 

 to the spore-bearing organ in general, has been often 

 applied in a narrower sense when that organ is well defined 



l<, 



.% 



\,'a\;.- 



Fig. 7. — -Stemonitis /• ■ ■ ,^ /. Li roup o£ sporangia. 

 X about eight diameters. 



and symmetrical, such as the grape-like structures of 

 Badhaiiiia (Fig. 1), the baskets of t'l-ihran'a (Fig. 5), or 

 the elongated forms of Arcijria or Stemouitis (Figs. (5 and 7). 

 jB. Plasmodiocarp is a term applied to the spore-bearing 

 part when it is sessile and irregular in form, sometimes 

 like a cushion, sometimes like a creeping snake or a long 

 tube. It may be said to represent the aggregated Plas- 

 modium which has stayed its onward course, gathered 

 itself together, covered itself with a coat, and then produced 

 spores. This form is shown at a, in Fig. 8. 



Fig. 8. — Crateriitm pedtmculatum. Group of Sporangia and 

 Plasmodiocarps. x about 10 diameters. 



y. J^thalium is the name given to that form of fructi- 

 fication in which a number of separate spore cases exist ; 

 but where they are so densely packed together, so 



intricately coiled, and so freely anastomosing that their 

 individuality seems to disappear. The Fuligo septica, the 

 mysie to which we have 



V 



/ 



.K.^^ 

 ^S^^^ 



Fig. 9. — Fuligo septica. Section 

 of mature iethalium. Somewhat 

 enlarged. 



already often alluded as 

 living on tan, and which 

 is known as the flowers 

 of tan (the only instance, 

 we believe, in which any 

 one of these organisms 

 has the slightest claim to 

 an English name), is 

 an instance of this 

 form of fructification. 

 Fig. 9 exhibits a sec- 

 tion of the mature fctha- 

 lium of Fuligo. 



Though it is both possi- 

 ble and convenient thus to 



classify the forms assumed by the fructification, it must 

 not be supposed that the lines between them are hard and 

 fast ; on the contrary, there are abundant instances in 

 which the plasmodiocarp and sporangium forms merge 

 into one another ; frequently the two forms will co-exist 

 as the products of one and the same plasmodium. 



Thus the beautiful little cups of Craterium will some- 

 times fail of complete separation, and part of the 

 Plasmodium is content to take the cruder form of a 

 plasmodiocarp, as shown in Fig. 8. Again, sporangia, 

 which are sometimes stalked, are at other times sessile, 

 and thus differ but little from a plasmodiocarp. In the 

 Dicti/ostelium (one of the Acrasiete to be hereafter men- 

 tioned), a similar phenomenon has been observed; although 

 in the normal form the production of spores occurs at the 

 top of the pedicel, or column, in some cases the Plas- 

 modium turns into 

 spores without ever de- 

 veloping the column 

 at all. 



There appears to be 

 a considerable difference 

 in the way in which the 

 Plasmodium turns into 

 sporangia. In some 

 cases the plasmodium 

 first separates, and then 

 each separate part 

 forms a sporan- 

 gium. In other cases 

 the Plasmodium be- 

 gins its transforma- 

 tion as a whole, and 

 breaks up into 

 sporangia as the 

 process advances. 



Comatricha and 

 Craterium appear to 

 be cases of the for- 

 mer mode of pro- 

 cedure ; Stctnonitisoi 

 the second. Thus in 

 Coniiitrichathe plas- 

 modium emerges in 

 separate centres, 

 like small conical 

 hillocks on the 

 wood. These grow 

 upward, and as they approach maturity the upper part of 

 the protoplasm draws aU the lower part after it, except so 

 much as goes to form the pedicel and hypothalkis, or foot. 



Fig. 10.— Sfemoiiilis fusca. 

 modium turning into Sporangia. 

 De Bary.) Enlarged. 



Plas- 

 (After 



