PROF. F. О. BOWER ON APOSPORY AND ALLIED PHENOMENA. 811 
shows that in many cases the arrested sporangia, the indusium, and even the swollen 
base of the sorus have turned brown, and are in process of decay; in others, however, 
green, actively living masses of tissue, often exhibiting a true prothalloid form, and 
bearing sexual organs, are to be found. Taking first the type (C), where the sporangium 
itself is the starting-point, there may occasionally be found single sporangia, among 
those already decaying, which retain active vegetative characters, and in which may still 
be recognized traces of those characteristic cell-divisions which are found in young stages 
of the normal sporangium; they are, however, masked by the repeated and less regular 
divisions accompanying the more active vegetative growth (fig. 31). These may be com- 
pared with arrested and vegetatively developed sporangia in Athyrium F.-f. clarissima 
(figs. 1-12), the similarity between them being very great. Such specimens illustrate 
the early stages of development of the type (C), which accordingly corresponds to that 
example of aposporous development which is found in Athyrium F..f. var. clarissima 
On such outgrowths from the arrested sporangium, antheridia may be found at a com- 
paratively early stage, and even before the outgrowth has assumed a truly prothalloid 
character. Thus in the specimen fig. 82 the apex of the outgrowth has developed 
directly as an antheridium, while a second antheridium is in course of formation in a 
lateral position ; this, it will be observed, is a very near approach to the formation of an 
antheridium actually upon the sporangium itself. Other examples are to be found in 
which the prothalloid outgrowth appears to be formed laterally from the stalk of the 
sporangium, while the actual head of the sporangium does not take a direct part: thus, 
in the section shown in fig. 33 this is the case, though it might perhaps be regarded as 
an intermediate form leading to the type (D), where the prothallus originates from the 
base of the sorus; in this example the apical part of the outgrowth had assumed dis- 
tinctly Ше prothalloid flattened character, but the basal portion was massive, and 
produced rhizoids and antheridia, one of the latter being represented in fig. 33 in a 
position but a few cells removed from the tissues of the typical sporophore. The speci- 
men fig. 35 may also be regarded as an intermediate between types (C) and (D), while 
that in fig. 34 seems to be clearly a case of outgrowth from the base of the sorus. 
Among other examples of the fourth type (D), one of the most prominent 18 shown in 
fig. 36, in which the initial activity is evidently in the base of the sorus: this consists 
of a mass of vegetatively active tissue from which rhizoids are formed, while laterally 
has been formed an elongated filament, bearing lateral rhizoids, and near its apex a 
flattened lateral expansion, which is already developing as a prothalloid structure, Аз 
far as the cultures have gone at present (Nov. 17, 1886), no archegonia have been found 
on prothalloid outgrowths from the sorus; but, since antheridia so frequently precede 
the archegonia on the prothalli of Ferns, it by no meats follows from this observation 
that they are throughout exclusively male. Lastly, bee may be stated that in some cases 
single cells, or groups of cells, of the indusium retain their active properties, while the 
rest die; these cells, with abundant chlorophyll in them, have been observed to put out 
r h repeated cell-divisions take place; but whether these may actually 
processes in whic жоие » | 
assume prothalloid characters and bear sexual organs, it is impossible at present to 
state. 4429 
