9 
actually split, and that through the cleft at one end the root-hair 
protruded, and at the other the first cell of the prothallium. The 
spores of the ferns of the genus Onoclea, as is usual in other ferns, 
are covered with a thick, dark brown exospore, or coat. (Fig. i.) 
In most ferns this remains attached to the basal cell of the prothal- 
hum, concealing a large portion of it, and, indeed, this is often the 
case in both O. Siriithiopteris and O, seusibilis, but in many cases in 
both ferns it is completely detached by the swelling of the spore in 
germinating, leaving the spore apparently covered only with a thin, 
transparent membrane (Fig. 2.) At the commencement of active 
growth, however, this membrane is seen to split along one side, and 
through the cleft thus formed the true endospore protrudes in the 
form of a root-hair at one end, and the basal cell of the prothallium 
at the other, which soon becomes separated from the root-hair by a 
transverse septum (Figs. 3 and 4.) In Fig. 4 the basal cell has 
become again divided so as to form two cells besides the first root- 
hair. ^ At this stage, with a little care, the two lobes of the second 
covering (Figs, 4 and 5, L) can be clearly seen. The edges of 
S. 
^hese lobes were the lines that puzzled me first. These lobes follow 
'^ nearly the lobes of the exospore, in those cases where it remains 
^^^^^^^^d. that it is then impossible to detect them. 
This accessory covering of the spore was first observed in O, 
^^^uthwpteris^ but, knowing the close resemblance of the spores of 
' ^^^^^ibilis^ to those of the former species, I conjectured that the 
same peculiarity might be detected in them, and experiment showed 
^hat this was the case. I have not detected it in other genera exam- 
*^ed, but, as in all cases, the exospore adhered so firmly to the spore 
fs to interfere seriously with observations, I do not think it at all 
^'^Possible that it does exist. 
These observations may be readily verified in either species, as 
^ spores germinate in a few days if simply placed in water and 
*^^pt in a warm place. 
the ^^'^'^^'^'^^ON OF Figures,— I. Spore of 0, Stnithiopteris still enclosed in 
Snn.^^^?^"^^^' 2. A similar spore in which the exospore has been cast off. 3. 
^'pore With iTiA ^*» — ^„i ^ ,f, ^, .__ .,_ ♦ i,„:. /.a f^ ^^r^^^-^.A^ a rHri*»r 
proth iT*'^'^ ^^^ second coat split, allowing the root-hair (r) to protrude. 4- 
O ..')^^-' s'^owing the lobes of the second coat (L.) 5. Similar prothalli 
Older 
uni of 
• ^ennhilis. All magnified 500 diameters. 
Douglas H. Campbell- 
