A Monogr,ix>b of the Genus Alaria. 43 



at a point in the sporopliyll-bearing region of the stipe, and is by 

 the median plane. Judging from a very young frond which has 

 a clearly divided stipe, the abnormity appears to have been caused 

 by a certain Influence at a point just below the transition point. 

 The frond develops farther adding a length to the stipe and thus 

 shifting the affected point further below the transition point. In 

 all specimens with such abnormity the two arms are nearly parallel 

 with very narrow sinus and have equal values. The sporophylls 

 may be found on the outer edges only of the two arms or on 

 both edges as well, and also below the furcation (Plate IV, figs. 

 4, 5). Similar cases have also been reported by Setchell^) on 

 A. esculenta Gkev., collected by Collins on the coast of New 

 England. In some examples the sporophylls are not particularly 

 different in number and size from the normal form, bat in many 

 cases, only a few of thenj, very irregular in size, are to be found. 



The blades on the two arms are not especially smaller than 

 the normal ones. In one case, however, one of the two blades 

 was destitute of its inner half, in spite of the midrib being as 

 broad as that of the complete blade. 



III. Other monstrosities. Besides the two kinds of monstro- 

 sities mentioned above there are various examples of deformation, 

 but of less importance. One of the common cases is the spiral 

 twisting of the sporophylls. This is undoubtedly caused by a 

 checking of growth in one side of a sporophyll while the other 

 side develops at normal speed. It may be due to an internal 

 cause in the tissue of the sporophyll or by an animal feeding on 

 the plant. In the Holosoria the spiral turning is mostly found 

 at the terminal portions of the sporophylls. 



Bifurcation of a sporophyll is also not rarely met with. An 



1) Setchell ; Eegeneration among Kelps, p. 149. • 



