Variation occurring in Biscutella laevigata. 



25 



in the remaining two they were absent altogether. Besides those of 

 Biscutella laevigata I examined the leaves of four other sub- 

 species (?) — viz., B. raphanifolia, B. ambigua, B. lyrata, and B. auricu- 

 lata, but I failed to discover any indication of lignification in the 

 mesophyll of these plants. 



Addendum, July 28, 1897. 



Since the foregoing paper was communicated to the Society, I have 

 myself visited the Val Formazza, and examined the character of the 

 Biscutella plants in this locality, and also in one or two Swiss 

 valleys. The results of these observations are given below : — 



Val Formazza, from the head of the valley down to the Tosa 

 Falls (5500 feet). 



In this reach of the valley the plants are abundant everywhere — 

 on the banks of shingle and sand and in the low-lying meadows near 

 the stream, and on the grassy slopes of the surrounding heights, up 

 to the Val Toggm on the one side, and as high as the lower limit of 

 the Hohsand Glacier on the other. Both the hairy and the glabrous 

 types were found, each variety often forming patches of varying 

 size ; such groups of dissimilar plants may occur side by side on 

 exactly similar ground ; or, on the other hand, a small area may be 

 occupied by both forms, which are indiscriminately mixed together. 

 On the whole the smooth individuals were more numerous thau the 

 hairy, especially in the low-lying meadows near the river, on the 

 steep slope up to the Val Toggia, and on the slopes on the opposite 

 side of the river between the chalets of Morasco and Riale. In the 

 above-mentioned meadows intermediate plants were also found, 

 especially the smoother forms, and though very few in number 

 compared with the extreme types, they were more numerous here 

 than in any other locality which 1 had the opportunity of observing. 

 Many of these intermediates were apparently young plants, and 

 their comparative abundance in this spot may, I think, be explained 

 by the fact that the season was a late one, and that consequently 

 some individuals were ranked as intermediates, wdiich had not yet 

 reached the stationary point, and which would eventually conform to 

 the smooth type. 



Val Formazza below the Falls and at Al Ponte (4200 feet). 



Here the plants were much fewer in number than in the upper 

 reach of the valley ; immediately below the falls they were almost 

 all smooth (no intermediates were seen) ; at Al Ponte the hairy and 

 the glabrous types were found together on the shingle near the 

 stream. 



