792 



coloured, granular mass, and finally separating from the frond. 

 Marine, or {more generally) found in fresh water streams, ponds and 

 ditches, or in damp situations. {The marine species of this sub-class 

 are alone described in the present work.)" — p. 4. 



K. 



On the Growth of Grass. By S. W. Leonard, Esq.* 



After some preliminary observations, the author stated that about 

 three years ago his attention was called to this subject, by observing 

 that some grass, which was in a vessel in which he kept some animal- 

 cules, increased in height very rapidly, one shoot which he measured 

 having grown as much as an inch and a half in twenty-four hours. 

 He consequently thought that, by proper management, he might pos- 

 sibly be enabled to see it grow under a microscope. Being prevented 

 at that time by other avocations from pursuing the subject, he was 

 unable to verify his idea until July last, when, having procured a turf 

 of the common meadow-grass {Poa annua), he manured it, and then 

 found it grew at the rate of an inch or more in twenty-four hours. 

 One of the young stems, with its root, was placed in a small test- 

 tube, which being properly adjusted under the microscope, he had 

 the satisfaction — with a power of 400 diameters — of seeing it traverse 

 the field of view. At first no motion was perceptible ; but in about 

 half a minute the point darted forwards considerably, and after re- 

 maining stationary for a short time it again made a spring forwards, 

 and so on at short intervals until it had entirely crossed the field. 

 This was repeated several times, with the same results. Suspecting, 

 however, that this mode of progression by starts could not be natural, 

 he made some alteration in the arrangement, and then found that the 

 motion forwards became gradual and equable. The field of the micro- 

 scope included rather more than -r^th of an inch, and the apex of the 

 grass traversed the whole diameter in somewhat less than ten minutes. 

 In reference to the mode of growth of this part of the plant, he stated 

 his opinion that a gradual expansion and elongation of the cells takes 

 place, causing the increase both in the length and breadth of the blade, 

 but that there might also be additional cells produced near the root, which 

 cells may be gradually developed and matured in the stem during its 



* Extracted from the ' Proceedings of the Microscopical Society,' published in the 

 ' Zoologist' for January. 



