128 THE AMERICAN MONTHLY. [July, 



Eastern forms. In specimens collected in a lake in the Uinta mountains, 

 Wyoming Territory, at 10,000 feet elevation, the brown hydra at first was 

 brick red, with a brighter red head, but, after keeping it for a week, it as- 

 sumed the pale brown hue as ordinarily observed in the animal nearer home. 



The characters of the two American forms, as observed by him, are as 

 follows : — 



Hydra viridis? The green hydra. Animal bright grass gi"een, some- 

 times paler. Body, when moderately elongated, cylindro-conical, tapering 

 towards the caudal end ; when contracted, oval or spheroid ; when greatly 

 extended, linear cylindrical. Head conical. Arms, four to seven, commonly 

 six, about half the length of the body, linear, capable of extension to about 

 the length of the bod}', or slightly more. In the sexually mature state : — 

 Testes hemispherical, surmounted by a nipple-shaped prominence, situated 

 on the sides of the body just below the arms ; ovary single, projecting from 

 near the middle of the body, and containing a single, spherical, white ^^^1 

 enclosed in a brownish covering. Animal usually three or four lines long, 

 capable of extension to twice the length, or contracting to less than a line. In 

 ponds and ditches in the vicinity of Philadelphia and other places, though not 

 common. Observed on one occasion in the sexually mature condition late in 

 autumn. In the individuals obsen'ed the sexes were separate ; the males 

 with the two testes, and the female with a single ovary. Tl^e ovum measured 

 0.375mm. in diameter. In the sexually mature H. viridis^ observed by 

 Prof. A. Thompson, individuals were hemaphrodite, while in others the 

 sexes were separate. 



Hydra fiisca? The brown hydra. Animal more robust than the former, 

 of the same shape and number of arms, but with the body less attenuated when 

 extended, and with the arms haliitually longer in proportion to the bod}', but 

 capable of extension to six times the length of the latter. Color usually pale 

 brownish, or reddish ; sometimes deeper, sometimes paler. In ponds, and 

 common on the under side of stones in the Schuylkill and Delaware rivers, 

 in the vicinity of Philadelphia. Not observed in the sexually mature condi- 

 tion. The color of the animal in a measure appears to depend on the nature 

 of the food ; and it may become a bright red, of variable tint, by feeding on 

 similar colored entomostraca, or insect larvte. From prolonged abstinence 

 the color fades and the animal becomes almost white. — Proc. Acad. Set. 

 Phil. 1 



The Bluck Spot.* 



By W. S. WINDLE. 



PURDUE UNIVERSITY, LAFAYETTE, IND. 



During the past few years much attention has been paid by florists to a dis- 

 ease of the rose known as the ' rose-leaf spot ' or ' black spot.' Upon close 

 examination it is ascertained to be a fungus, and is termed Actinonema rosce. 

 Apart from its scientific interest this spot claims special attention, since it pro- 

 duces a premature falling oft' of the leaves, especially of the cultivated varieties. 

 The growth of the fungus is most rapid during the cold and moist weather ot 

 autumn. It thus becomes very annoving, for, owing to the early falling of the 

 leaves, the rose goes into a premature rest. Often when the cool and moist 

 weather continues }'oung sprouts are put out from the upper buds of the twigs 

 and perish in the winter. 



In its early stage this fungus has a characteristic appearance. It first ap- 



* Reprinted from the American Florist, vol. iii, No. 66, May i, 1888, to which journal we owe the use of the 



figures. 



