370 French National Instiiute. 



in plants of the same family, he deduces rules from which 

 agriculture may derive great advantage in stopping this kind 

 of c>)ntagion. 



Before M. de Candollc's time, we were acquainted with 

 81 of these nnishruoms : his observations have increased 

 this number to 100. 



In a memoir upon marine algce he shows that these plants 

 have not any real roots ; that in their organization there is 

 no trace whatever of vessels ; that tliey absorb humidity 

 throughout their whole surface ; that the more green they 

 are, the more oxygen gas thev liberate in the light ; he an- 

 nounces that the small grains, hitherto regarded as their 

 seeds, are only the capsules of them, and contain grains 

 much smaFier, coaled with a viscous matter, which tixes 

 them V. here they are to germinate. 



Lastly, M.de Candolie has presented a memoir, in botany 

 properly so called, upon the family of the rubiacece, which 

 he divides into four orders, and to which h§ adds four new 

 genera. 



M. de Petit-Tho'.sars has resided a long time in the isles 

 of France and Bourbon, and has made a voyage to Mada- 

 gascar. He has begun to publish the Flora of the latter, 

 which is very rich in singular plants ; in particular, he has 

 made some valuable observations upon the orchidece, plants 

 which must be examined while in life, and which refuse all 

 cidtivation. He is ready to publish a great number of new 

 species of these plants. The ferns have also been a pecu- 

 liar object of his inquiries. The island of Madagascar alone 

 su])plied him with 89 jiew genera, the characters of which 

 he is about to print, and which he sent into France ten 

 years ago. His observations upon the germination of the 

 cycas led. him, to discover that this singular tree, which some 

 call a Jtrn, and others a palm-tree, ought to constitute a 

 dislincl family. 



The draccena ox candle luood has made him acquainted 

 with particular facts, extremely curious, which led him to 

 a general and new system upon the development of trees. 

 We shall endeavour to give an idea of it. 



Wc know that the trunk of ordinary trees increases from 

 4 the 



