234 



THAXTER. MONOGRAPH OF THE LABOULBENIACE^E. 



developed aquatic species of the genus Laboulbenia. It is therefore among the Ceratomycetinese, of 

 the accompanying Key, that one would look for suggestions in this connection. That the vegetative 

 characters of this series, far from being simple, are quite the reverse, might have no significance in this 

 respect; but if one presupposes an origin for the group from aquatic types near the simpler Floridese, it 

 is evident that in these water forms, the antheridial characters, which afford by far the most reliable and 

 fundamental characters for general groupings in these plants, are more unlike the antheridia of the red 

 alga 3 than those of the more highly developed terrestrial genera. In any attempt to arrive at a conclusion 

 concerning these matters, several fundamental questions need answers which are not as yet forthcoming. 

 First, has the unspecialized antheridial cell of Rhyncliophoromyccf! or Zodiomyces, for example, become the 

 specialized cell of the Laboulbeniacese, through conditions which may be suggested by those found in 

 Coreomyces; or has the passage been in the reverse direction, resulting as an adaptation more likely to 

 insure fertilization under the conditions of aquatic life. The second supposition, indeed, seems by no 

 means an unlikely one, and Ceratomyces, which is assumed, at least, to produce its sperm-cells in coherent 

 threads, would represent the culmination of this tendency in a modern genus. 



Again it may be asked whether the simple antheridium has been derived from the compound, as 

 might be suggested by the conditions seen in Disticliomyces, or by a reduction to one cell of such a com- 

 pound antheridium as is found in Riekia: or, as seems more probable, has the reverse process actually 

 occurred. Furthermore it is by no means evident whether the unisexual, or the hermaphrodite condition, 

 which are associated with both the simple and compound type of antheridium, is primitive or the reverse. 

 Although the general tendency in upward series appears to be toward a separation of the sperm- and 

 egg-cell-function on different individuals, and this condition has no exceptions in the highest plants, by 

 far the most highly developed and apparently modern genera of Laboulbeniales are hermaphrodite: 

 but if we look for what is absolutely the simplest condition found in this group, we find it without question 

 in the genus Amorphomyces, a unisexual type with simple antheridia. And here it may be pointed out 

 that all the forms which grow on Blattidse, supposed by entomologists to be among the most ancient types 

 of insects, are unisexual, with simple antheridia. 



The not uncommon phenomenon already mentioned above, and formerly illustrated in Laboulbenia 

 inflate, Monograph, Plate III, fig. 5, which involves the atrophy of one member of the usual spore- 

 pair, may be perhaps significant in this connection ; in that it suggests the survival of a tendency to form 

 two kinds of individuals, one of which had become superfluous after the appearance of antheridia on the 

 female individual. This is still more strikingly suggested by instances such as the one illustrated here- 

 with, on Plate XLIX, figs. 16-17, which, although rare in general, are common in this and a few other 

 species. Here one member of the spore-pair, becomes not only a dwarf individual, but is absolutely 

 unisexual, bearing a well developed and normally functional antheridial appendage. Yet here also, 

 the monopolization of food supply by one member of the spore-pair, may have led to a dwarf habit and 

 partial loss of function in the other, and it is not by any means inconceivable that, through gradual loss 

 of its male function by the vegetatively vigorous individual, a unisexual condition might become a fixed 

 phenomenon, in both members. 



Since the series may thus be read upward or downward as one prefers, and Amorphomyces is quite 

 as likely to illustrate a last step in retrogression as a first in evolution, one may be pardoned, if like the 

 writer he confesses his complete agnosticism in these matters, an agnosticism which embraces the question 



