58 CIRCUMNUTATION OF SEEDLINGS. CHAP t 



Cycas-pedinata (Cycadese). The large seeds of this plant in 

 germinating first protrude a single leaf, which breaks through 

 the ground with the petiole bowed into an arch and with the 

 leaflets involuted. A leaf in this condition, which at the close 

 of our observations was 2j inches in height, had its movements 

 traced in a warm greenhouse by means of a glass filament 

 bearing paper triangles attached across its tip. The tracing 

 (Fig. 45) siiivws how large, complex, and rapid were the circum- 



Fig. 45. 



Cycas peotinata : circumnutation of young leaf whilst emerging from the 

 ground, feebly illuminated from above, traced on vertical glass, from 

 5 P.M. May 28th to 11 A.M. 31st. Movement magnified 7 times, here 

 reduced to two-thirds of original scale. 



nutating movements. The extreme distance from side to side 

 which it passed over amounted to between '6 and '7 of an 

 inch. 



Cauiut, \7arscewiczii (Cannacese). A seedling with the plu- 

 mule projecting one inch above the ground was observed, but 

 not under fair conditions, as it was brought out of the hot- 

 house and kept in a room not sufficiently warm. Nevertheless 

 the tracing (Fig. 46) shows that it made two or three incom- 

 plete irregular circles or ellipses in the course of 48 hours. The 

 plumule is straight ; and this was the first instance observed 



