Helminthostachys zeylanica . 185 
when the spores are entirely separated and mature, the tapetum disappears.’ 
In Helminthostachy s the tapetum and tapetal nuclei are evidently more 
persistent than Cardiff found to be the case in Botrychium l . It has already 
been mentioned that the plasmatic membranes and many nuclei are still to 
be found between spores which are quite or nearly mature, and I have 
rarely found nuclei which w'ere degenerating except in sporangia which 
were almost ready to dehisce. In such sporangia the majority of the 
nuclei stained intensely and were closely packed with chromatic granules, 
whilst here and there a nucleus was seen in which the nuclear membrane 
had disappeared and the granules were becoming dispensed (Fig. 13). 
Mitotic divisions of the tapetal nuclei were at no time seen. 
Cardiff records frequent amitotic divisions of the tapetal nuclei of 
Botrychium , but Stevens was unable to confirm this observation. 
In Helminthostachys I have found reason to believe that in the early 
stages of sporangial development, immediately after the tapetal membranes 
have disintegrated, the nuclei do multiply by direct division, but in older 
sporangia it is much more difficult to find any evidence of such divisions. 
Irregularities in outline, which sometimes lead to a more or less constricted 
shape, not uncommonly occur, but most of these are undoubtedly to be 
referred to those passing changes of form which are so frequently to be 
found in nuclei that are taking part in active metabolic processes. 
Occasionally these changes of form may actually lead to a division of the 
nucleus, but in my material this is certainly rare. An isolated instance of 
such a division is shown in Fig. 14. Very possibly the conditions which 
prevail at the time when the material is collected may exert an influence 
upon the tapetal nuclei and may explain the differences which occur in 
the accounts of Cardiff and Stevens. 
The principal features, therefore, which the tapetal plasmodium 
presents during the period of exospore growth are (a) an almost or quite 
complete disappearance of starch, (b) a gradual diminution of the finely 
vacuolar cytoplasm, and (c) the richly chromatic nuclei which often show 
irregularities of outline. 
These features, I think, bear out the view already expressed that the 
tapetal plasmodium is the centre of metabolic activities in which a sub- 
stance is elaborated from the raw materials contained in the tapetum. 
For reasons already stated we may further conclude that this substance is, 
directly or indirectly, employed in the growth of the spore-wall. 
1 Stevens also records much greater persistence of the nuclei in the Botrychium examined 
by him. 
