NOTES AND MEMOKANDA. 67 



elements are ectodermal ; in Hydractinia (Van Beneden) the ova are 

 eadodermal and the spermatozoa f ctodermal ; lastly, in Eudendrhim 

 (Ciamician) the ova are ectodermal and the spermatozoa endodermal. 

 Ciamician supposes that the generative products arose in the first 

 instance indifferently from either layer, and that by further develop- 

 ment they left their original position and came to lie between the two 

 lamellae. 



Sir Joseph Hooker on the Modern Development of Micro- 

 botany. — Sir Joseph Hooker devoted part of his address as President 

 at the last anniversary meeting of the Royal Society to the modern 

 development of botanical science, there being, as he pointed out, 

 perhaps no branch of research with the early progress of which the 

 Society was more intimately connected. 



" One of our earliest secretaries, Robert Hooke, two centuries agOj 

 laboured long and successfully in the improvement of the microscope 

 as an implement of investigation. He was one of the first to reap 

 the harvest of discovery in the new fields of knowledge to which it 

 was the key, and if the results which he attained have rather the 

 aimless air of spoils gathered hither and thither in a treasury, the 

 very fulness of which was embarrassing, we must remember that we 

 date the starting-point of modern histology from the account given 

 by Hooke in his ' Micrographia ' (1667) of the structure of cork, 

 which had attracted his interest from the singularity of its physical 

 properties. Hooke demonstrated its cellular structure, and by an 

 interesting coincidence he was one of the first to investigate, at the 

 request, indeed, of the founder of the Society, Charles II., the 

 movement of the sensitive plant Mimosa imdica, one of a class of 

 phenomena which is still occupying the attention of more than one of 

 our Fellows. In attributing the loss of turgescence, which is the 

 cause of the collapse of the petiole and subordinate portions of the 

 compound leaf which it supports, to the escape of a subtle humour, 

 he to some extent fi -reshadowed the modern view which attributes the 

 collapse of the cells to the escape of water by some mechanism far 

 from clearly understood — whether from the cell-cavities or from the 

 cell-walls into the intercellular spaces. 



Hooke having show^n the way, Nehemiah Grew, who was also 

 secretary of the Eoyal Society, and Marcello Malpighi, Professor of 

 Medicine in the University of Bologna, were not slow to follow it. 

 Almost simultaneously (1671-3) the researches of these two inde- 

 fatigable students were presented to the Eoyal Society, and the 

 publication of two editions of Malpighi's works in London prove how 

 ertirely this country was at that time regarded as the head-quarters 

 of this branch of scientific inquiry. We owe to them the generaliza- 

 tion of the cellular structure, which Hooke had ascertained in cork, 

 for all other vegetable tissues. They described also accurately a 

 host of microscoiiic structures then made known for the first time. 

 Thus, to give one example. Grew figured and described in several 

 different plants the stomata of the epidermis : — ' Passports either for 

 the better avolation of superfluous saji, or the admission of air.' 



With the exception of Leeuwenhock, no observer attempted to 



F 2 



