320 ANNUAL OF SCIENTIFIC DISCOVERY. 



exposed to all the rays of the solar spectrum ; the next greatest was 

 under the blue glass. Wheat was also grown in a similar manner ; 

 the method of arrangement of apparatus being minutely detailed, and 

 the character of the corn plants which appeared under the various 

 glasses. Those under the yellow were the most sturdy in their 

 growth ; those under the blue the least healthy ; whilst some grown 

 under a nearly darkened shade grew quickly nine inches long, put 

 forth no secondary leaves, and died in a month. Mallows were grown 

 in a similar manner. The detailed observations were of much the 

 same purport as in the preceding instance. As it had been formerly 

 observed by the author and his brother, that plants kept in an 

 unchanged atmosphere appear to enter into a sort of lethargic condi- 

 tion, experiments were instituted for the purpose of ascertaining 

 whether the alteration in light produced by colored media made any 

 marked variation in this matter. The pansy and the Poa annua were 

 the plants selected ; and comparative experiments were made with a 

 darkened shade, and with no covering at all. The results were vari- 

 ous, but scarcely conclusive, unless in reference to the fact that 

 plants survive much longer for being in unchanged air. The color- 

 less and yellow media appeared most favorable to the healthiness of 

 the plants. As experiments on growing plants must stretch over a 

 considerable time, the author's observations were not put forth as foun- 

 dations for any generalization, but just as samples of his preliminary 

 attempts. 



ON THE MORPHOLOGICAL ANALOGY BETWEEN THE DISPOSITION 

 OF THE BRANCHES OF EXOGENOUS PLANTS AND THE VENATION 

 OF THEIR LEAVES. 



PROF. Me COSH, at the British Association, brought forward an 

 interesting communication on this subject, and endeavored with great 

 ingenuity to generalize and reduce to a common law the peculiarities 

 which are manifested in the branching of exogenous plants, starting 

 with the theory propounded by Goethe, that all the appendages of 

 plants, whether leaves, bracts, sepals, petals, or stamens, are formed 

 after a common type, and that that type is the leaf. Prof. Me Cosh 

 attempted to show that this theory might be extended further, and 

 that the type of the leaf is not only that of all the appendicular organs, 

 but of the buds and of the branches, and therefore eventually of the 

 whole plant itself. The leaf is to the plant as the microcosm to the 

 macrocosm it is the plant in miniature a common law governs the 

 two, and therefore whatever disposition we find in the parts of the 

 leaf, we may expect to find in the parts of the plant, and vice versa. 

 Now, the veins of the leaf are the analogue of the branches of the 

 plant, and therefore the venation and the ramification must essentially 

 harmonize with one another. In illustration of the law, the Professor 

 pointed out that in reticulated leaved plants (to which alone he 

 referred) there is a correspondence between the distribution of the 

 branches along the axis, and the distribution of the venation of the 



