BOT.— Vol. II.] HUS—PORPHYRA. 1 89 



These monospores can easily be distinguished from the dead 

 vegetative cells lying among the sporocarps. The dead 

 cells possess likewise a thick wall but apparently contain 

 yellowish, homogeneous, highly refractive cell-contents, in 

 which no chromatophore can be discerned. 



Whether monospores are sexual or not, or whether they 

 possess any reproductive power, the author has, notwith- 

 standing a series of careful experiments, been unable to 

 determine. 



The reproductive bodies are usually first formed at the 

 margins and gradually spread over the whole frond. Bornet 

 even observed spores in the basal cells of P. laciniata. 

 Under the microscope we can trace the various stages of 

 division from the original vegetative cell to the fully ripe 

 sporocarp. This is especially easy in the species where 

 antheridia and sporocarps occur side by side in patches. 

 Observation shows that each vegetative cell gives rise to a 

 single sporocarp. The sporocarp by two more or less 

 simultaneous divisions at right angles to each other and to 

 the surface of the frond finally consists of four segments. 

 In some species division proceeds no farther, and four carpo- 

 spores are the result; but in other species, where the fully 

 ripe sporocarp contains more than four carpospores, the 

 cruciate division is followed by a division parallel to the 

 surface of the frond, giving rise to eight segments, which 

 by further cruciate division perpendicular to the surface of 

 the frond in each of the resulting cells may give rise to 

 thirty-two carpospores.^ 



In the formation of the antheridia, starting from the vege- 

 tative cell equivalent to the mother-cell of a sporocarp, there 

 first takes place a vegetative cruciate division perpendicular 

 to the surface of the frond, which gives rise to four anther- 

 idial cells. Consequently, owing to this additional vegetative 



iThe author understands under "cruciate" division, two divisions in diflFerent direc- 

 tions, at right angles to each other and to the surface of the frond, and which are simul- 

 taneous or nearly so. Under "transverse" or "parallel" division the writer understands 

 a division parallel to the surface of the frond. Though these divisions are, of course, 

 but seldom if ever strictly parallel or at right angles, the use of the terms "cruciate " 

 and "parallel" is a great convenience, doing away with a lengthy explanation. 



( 2 ) December 19, 1901. 



