210 BOTANICAL GAZETTE ’ [SEPTEMBER 
there is a great mortality among the spores, which, as can be readily seen, 
vary greatly in size. Among the first things to establish in this and. similar 
cases, is whether mortality is greatest among the smaller or larger spores, and 
whether the prothallia springing from the smaller spores tend to remain small 
and produce only antheridia, while the larger female plants arise only from the 
larger spores, and so on. 
The fern in question was Onoclea Struthiopteris, although the 
name of the plant was not stated in the address in question. 
Miss Wuist (op. cit. p. 217) states that about 1 per cent of the 
prothallia of soil cultures were monoecious. This estimate seems 
to me to be much too low, inasmuch as an examination of a larger _ 
number of prothallia, since the publication of the paragraph just 4 
quoted, showed that about 12 per cent were monoecious. The =& 
prothallia from which this estimate was made were grown upon 
soil under good cultural conditions. The plants, although grown 
thickly, were vigorous, normal in every way, and in fact the 
cultures seemed to leave nothing to be desired. The monoecious 
prothallia were as a rule young, beating one to several archegonia, 
and were 1.5-3 mm. in diameter. Antheridia were very rarely 
found on older and larger prothallia, although little attention 
was paid to exact size and measurement. The antheridia were 
as a rule upon the ventral side, among or near the rhizoids, hence — 
upon the older tissue; very rarely did they appear at the margin 
of the prothallium. In one case an antheridium was found upo? 
the archegonial meristem. : 
In determining whether prothallia were monoecious, I did not 
rely at all upon an examination of fresh material, but all plants — 
were carefully fixed, stained im toto with borax carmine, cleared, 
and examined in clove oil or balsam. In this way a single sma — 
antheridium could easily be found upon a prothallium, and case — 
were not infrequent of a single antheridium appearing inconspicy" 
cleared, one may also more readily and accurately detect very 
small male plants adhering among the rhizoids of the larget P¥™” 
thallia bearing archegonia. 
In order to ascertain whether crowding was in any Way 
