Prof. Williamson : Annual Address, Y. N. U. 



99 



natural system, which, however, was very imperfect. Then came the 

 younger Jussieu, who laid hold of Lobel's discovery, and on it based 

 the two grand classes of flowering plants, the Dicotyledons and the 

 Monocotyledons, or those having two and one seed-leaf respectively. 

 Desfontaine next discovered the connection between the dicotyledo- 

 nous mode of germination and the exogenous method of stem growth. 

 (The Professor here enlarged considerably upon this connection, 

 adducing Tarious examples.) The next great discovery was partly 

 morphological and partly physiological, and was made by a man from 

 whom we should scarcely have expected it a priori. But (loethe had 

 the spirit of a scientific philosopher, and he showed that the flower is 

 morphologically a leaf-bud, and that every part of every flower is 

 merely a modification of an ordinary leaf. Gardeners know how easy 

 it is in many cases to cause a plant to be so prolific in flowers that 

 the ordinary foliage is almost hidden. The reason of this is, that the 

 ordinary buds are converted into flowers. 



Another discovery was now made. When a flower is young, its 

 component parts are regular, all the whorls having frequently the 

 same number of parts and being symmetrically arranged. But De 

 CandoUe showed that by the suppression of certain parts, the 

 cohesion of parts, and the increased development of others, we have 

 irregular flowers, like the pea and the snapdragon, developed from 

 regular ones ; and Dr. Robert Brown deserves and receives the 

 highest praise for his investigations into the development of the 

 flowers of orchids, which was especially a brilliant achievement by a 

 man the whole of whose work was well done. 



The Professor then passed on to the consideration of the Crypto- 

 gams, or so-called flowerless plants. Linneeus found many plants in 

 which he could discover no trace of a flower, such as ferns, mosses, 

 &c., but he very wisely called them cryptogamic, and not agamic — 

 flowers hidden, not flowers absent. Up to 1840 men sought in vain 

 for the reproductive organs of the cryptogams, simply because they 

 looked in the wrong place. To Nagel is due the honour of having 

 first discovered it among ferns. The first growth from a fern spore 

 is a small dark-green cellular film, about the size of one's finger nail, 

 which we call the prothallium, and this bears the organs which 

 correspond to the stamens and pistils of flowering plants. Nagel 

 discovered the antheridia, or male organ, in 1844, and a Polish 

 Count the archegonia, or female, in 1848. Since then, a host of 

 observers have made one discovery after another, until this depart- 

 ment of botanical science has been brought into its present state. 



