48 



they must belong to the same genus. I cannot, however, 

 find any combining character, and their differences are very 

 numerous. 



101. GONG(5RA maculata; var. alba. 



Among the Orchidaceous plants received by the Horti- 

 cultural Society from Oaxaca, a singular variety of Gongora 

 has made its appearance, with all the habit of the original, 

 but with flowers almost white, except some pale dull wine- 

 coloured spots on the sepals. It is a very graceful thing, and 

 forms a good contrast with the old yellow and purple kinds. 



NEW VIEWS CONCERNING STARCH. 



In the last number of the Annales des Sciences there has 

 appeared a very interesting paper by Mr. Mohl, concerning 

 the action of iodine upon the elementary organs of plants. 

 We hardly need inform our readers that starch is a product 

 of the vegetable kingdom, found in the shape of oblong bodies 

 of various sizes in the interior of cells, and that it has the 

 property of becoming blue if acted upon by iodine ; which 

 immediately detects its presence. It has also been supposed, 

 up to the present time, that starch is the only known sub- 

 stance whose colour is thus affected when acted upon by 

 iodine. It appears, however, from the researches now before 

 us, either that other substances are so acted upon, or that 

 starch exists in other states than that of the granules just 

 spoken of. 



Schleiden had remarked, that when cells are boiled in a 

 ley of caustic alkali till they are dry, they are stained blue by 

 the action of iodine, but lose the property by a prolonged 

 ebullition in water. He did not however absolutely admit 

 that by this process the lining of cells is changed into starch, 

 but he thought it most probably was so, because when weak 

 sulphuric acid acts upon vegetable tissue, and iodine is added, 

 a small quantity of iodide of starch is obtained. He supposes 

 that by this operation the primitive membrane of cells is also 

 changed into starch. He also considered that when woody 

 tissue is converted into gum and sugar by the action of sul- 

 phuric acid, that action is secondary, a conversion of it into 

 starch always taking place in the first instance. Schleiden 



