18 DOUGLAS HOUGHTON CAMPBELL ON THE 



Section I. Prothallium. 



The spores are of the so-called bilateral form, oval in shape and protected by a fii-m, 

 dark brown outer coat, the exospore, whicli is provided with ridges or folds, usually ar- 

 i-anged so as to enclose au irreg-uhirly polygonal area, other i-idges ruiuiing from the an- 

 gles. The spore is slightly flattened on ttie side originally in contact with its fellow, in 

 the mother-cell, and the exospore on this side is smooth. Besides the exospore there are 

 two other coats: a middle one that does not appear to have been previously noted in 

 ferns, and the endospore. The middle coat is not readily seen before germination, but 

 that it is not unmodified cellulose is shown by the ftict that the prolonged action of sul- 

 phuric acid and iodine does not color it blue. It is plainly seen in cases where the opaque 

 exospore has become detached before germination, as it must be ruptured before the en- 

 dospore can protrude. The exospore seems to be only slightly attached, readily separat- 

 ing on slight friction, and is often thrown off by the swelling of the spore on the absorption 

 of water. 



On examining dry spores after the removal of the exospore, they are found to be flat- 

 tened on one side, but in a few minutes after being placed in water, by its absorption they 

 become distended and all trace of flattening disa[)pcars, the spore then being almost per- 

 fectly oval in form (PI. 4, fig. 1). Thej^ contain abundant chlorophyll which is some- 

 times nearly uniformly distributed throughout, but is commonly more abundant in the 

 center. Besides the chloi-ophyll, the protoplasm contains other granules, not, however, 

 of starch. Oil is often to be detected in drops of considerable size but is usually uni- 

 formly distributed. At the center of the spoi'c, but usually nearly concealed by its dense 

 contents, is a small, but sharply defined nucleus 



Under favorable circumstances, the spores begin to germinate in from three to five days. 

 The early stages can best be observed by simply growing the spores in water, and keep- 

 ing them in a warm place in a moderately strong light; but perfect prothallia cannot be 

 thus obtained. 



The first sign of germination, in cases where the exospore has been thrown off, is a 

 splitting of the second, or middle coat, for neai-ly the whole length of the spore, and 

 through the fissure thus formed the endospore protrudes (PI. 4, figs. 2, 3). Usually 

 one end of the spore at this time is more transparent than the rest, being wholly, or in 

 part, destitute of chlorophyll. This transparent end becomes shut oft' from the body of 

 the spore by a septum nearly at right-angles to the longer axis of the spore, and becomes 

 the first root-hair (PI. 4, figs. 2-4, G). This elongates rapidly, attaining in the course 

 of two or three days four or five times the length of the original spore. The body of 

 the spore has also elongated by this time to more than twice its original size, and becomes 

 further divided by a septum nearly parallel to the first. The terminal cell continues to 

 increase in length, and new septa parallel to the first are formed thus causing the pro- 

 thallium to assume the filamentous or j^rotonemal stage (PL 4, figs. 4, 6). By the 

 end of the first week many of the prothallia show divisions at right angles to those first 

 formed, this sometimes occurring in the second or third cell, but not usually until a row 

 of three or four cells has been formed. About the same time a second root-hair is formed 

 from the basal cell. A small papilla is formed on one side which is cutoff from the cell 



