52 NOTES AND MEMORANDA. 



comparison of the nucleus to the sporangium and to the pollen sac, 

 confirms the results which we have obtained by the comjiarative study 

 of the carpel. 



The insertion of the nucleus on a leaf is proved for the Gymno- 

 spei*ms and a part of the Conifers ; it may also be admitted in a 

 general way for the other part of this family, but the details are still 

 unknown. 



The Gymnosperms, however, differ notably from the Angiosperms 

 in several points, and constitute a separate branch which has not the 

 same origin. The following are some of the differences which separate 

 them : the forcing down of the female sporangium ; the origin of the 

 integument in two primordial points in a part of the genera ; the 

 development of the proembryo and the embryo ; the disposition of the 

 pollen sacs, and (in part) of the ovules on the staminal or carpellary 

 leaf. 



As the pollen sacs, wherever their position has been clearly recog- 

 nized, are borne on the leaves ; as all the facts, in the obscure cases, 

 seem to indicate the same thing ; as that is true for the ovule ; as the 

 sporangia of the Cryptogams, the common and primitive form of the 

 phanerogamous reproductive organs, are equally developed on leaves, 

 it must be admitted as a general rule that the reproductive organs of 

 all the vascular plants are borne on the leaves, and that morphologi- 

 cally they are metablasts. 



I shall be pleased if this memoir should contribute to the general 

 acceptance ere long of the theory of Brongniart, the only true and 

 admissible one — that I am now convinced of it is due in great part to 

 the ingenious Slave botanist, Ladislao Celakovsky.* 



Laboratory for Microscopic Work. — In the Zoological Laboratory 

 at Newport, Ehode Island, U.S., recently established by Professor 

 Alexander Agassiz, the tables for microscoj)ic work are three-legged 

 stands, of varying height, adapted to the different kinds of Micro- 

 scopes in use. The whole of the northern side of the floor upon 

 which the work-tables and microscope-stands are placed, is sujiported 

 upon brick piers and arches independent of the main brick walls of 

 the building, which form at the same time the basement of the 

 building. The rest of the floor is supported entirely upon the outside 

 walls and upon columns with stretchers extending under the crown of 

 the arches reaching to the northern wall. This gives to the micro- 

 scopic work the great advantage of complete isolation from all 

 disturbance caused by walking over the floor. This will be duly 

 appreciated by those who have worked in a building with a wooden 

 floor, where every step caused a cessation of work and was sure to 

 disturb any object just at the most interesting moment. f 



A New Micrometer. — Spider-line micrometers, or micrometers of 

 fine threads of platinum, are inconvenient from the thickness of the 

 threads, from their expansion or contraction under thermic or 

 hygrometric influences, from the difficulty of fixing them parallel to 



* ' Ann. tics Se. Nat. (Bot.),' 6th series, vol. v. p. 250. 

 t ' Am. Jour. Sci. aud Arts,' vol. xvi. p. 488. 



