PROF. F. О. BOWER ON APOSPORY AND ALLIED PHENOMENA. 305 
the specimen shown in fig. 3 the annulus had already been formed, though its cell-walls had 
not become thickened ; here the cells of the head of the sporangium had almost lost their 
contents, whilst those of the stalk (s¢.) have abundant protoplasm and chlorophyll gra- 
nules. If any substitutionary growth were assumed at all in so old a sporangium, it 
would probably be in the stalk; but no instance has been observed of a sporangium, 
developed so far as to show a clearly marked annulus, assuming a substitutionary vegeta- 
tive growth. It is therefore concluded that in these sporangia the arrest of the normal 
development is complete and final. 
In other cases, not so far advanced as fig. 3, it has been observed that the whole head 
of the sporangium is finally arrested, while the substitutionary growth appears in the stalk 
only (figs. 4, 5). An examination of fig. 4 will show that, though the archespore itself 
has not divided, the cells forming the wall of the sporangium have undergone more divi- 
sions than in such a specimen as fig. 6, while that more advanced development (fig. 4) is 
followed by the complete arrest of the head of tbe sporangium ; the stalk, however, has 
assumed active vegetative growth. The same has probably been the case with the speci- 
men shown in fig. 5, though the body (л), which is probably the head of the sporangium, 
is here so shrivelled that the actual cell-divisions in it could not be stated with certainty. 
In these examples of arrest at а later stage of the normal development it is clear that, 
since the whole head of the sporangium is aborted, the archespore takes no part in the 
further growth ; this is, however, the case also for the large majority, if not for all, of the 
sporangia which are arrested at earlier stages. A comparison of the series of figs. (1-7) 
will show clearly that in all cases where the archespore is distinguishable at all, it pre- 
serves its identity without undergoing further divisions ; and, indeed, it is very frequently 
possible to recognize the archespore, as a brown dead cell, in growths of very considerable 
size produced from early-arrested sporangia. These facts possess some interest, as showing 
that the cell from which the spores are derived is specifically a spore-forming cell, and is 
not (at least in the large majority of cases, if not in all) in a position to assume other 
functions. 
Turning now to the description of the substitutionary growth as shown in examples of 
earlier arrest, it is seen that here the whole head of the sporangium is not aborted and 
thrown off, but that the superficial cells of it take an aetive part in the substitutionary 
vegetative growth. The starting-point will be sporangia such as those represented in 
Во. Зв, с. In these the archespore is easily recognized ; in some cases the number, form, 
and arrangement of the cells closely correspond to the normal (А); in others there are 
recognizable, even at this early period, cell-divisions which are not normal, together with 
a general elongation of the sporangium and arrest of the archespore. These foreshadow 
that purely vegetative development which they ultimately assume in place of the normal. 
Not unfrequently one or more cells of the head of the sporangium assume a brown colour 
and appear inactive; in other cases, as the results of further culture show, the whole 
series of superficial cells take part in the development. Thus in fig. 6 all the superficial 
cells of both stalk and head show active properties, being well supplied with protoplasm 
and chlorophyll, which, however, are absent from the archespore (a). These characters, 
