176 



THE AMERICAN MONTHLY 



[September, 



the uncertainty of the microscopical 

 evidence taken alone — -it may be justly 

 maintained that such evidence is, to 

 say the least, not infallible. The sub- 

 ject having been brought before the 

 public once more, it seems desirable 

 that microscopists should be reminded 

 that the microscope cannot be regarded 

 as infallible to distinguish human 

 blood. It may be we are conservative 

 about it. We are willing to believe 

 that the microscope is capable of 

 identifying human blood from the 

 examination of a few dried corpuscles, 

 but the proof that it is so, seems to us 

 not conclusive. If we err it is upon 

 the side of safety ; and to those read- 

 ers who have had no practical acquaint- 

 ance with such examinations, we would 

 say, do not be led into error by the 

 apparent simplicity of the problem. 

 If human blood can be identified with 

 the microscope, it can only be done 

 with safety by persons of great experi- 

 ence in the examination and measure- 

 ment of blood-cells. 



We should be pleased to receive 

 from a large number of our subscribers 

 samples of the new " Postal Note ;"' — 

 a note of the value of $1.00 can be 

 purchased for a 3c. stamp in addition 

 to the dollar, and is a safe and con- 

 venient means of sending money. 



Spirogyra. — In all specimens of 

 this beautiful alga with longitudinal 

 spiral bands of chlorophyl, a nucleus 

 can be observed near the middle of 

 the cells, and if a favorable view is 

 obtained it will be seen that from the 

 nucleus radiating and branching 

 threads of colorless, minutely granular, 

 protoplasmic matter extend in all di- 

 rections. It has been supposed that 

 these threads of protoplasm extended 

 to the layer of protoplasm lining the 

 walls of the cells, but Pringsheim 

 has observed tiiat this is not true. 

 They pass to the inner surface of the 

 chlorophyl-bands, and there end in a 

 trumpet-like expansion which encloses 



a granule of starch, or if there is no 

 starch-grain to be seen at the spot, it 

 may be expected to appear there very 

 soon. The threads may divide and 

 then two granules of starch will be 

 formed where the branches reach the 

 chlorophyl ; or the starch-grains 

 themselves may divide and separate, 

 which will also cause a forking of the 

 protoplasmic thread. In the latter 

 case the two amylum-bodies will be 

 also connected by a lateral extension 

 of the protoplasm forming a bridge 

 between them. 



We commend these observations to 

 our readers as worthy of verification. 

 Spirogyra is a beautiful plant to study 

 and is easily obtained. It will grow 

 for weeks in a saucer of water. We 

 can freely say that whoever attempts 

 to verify the work of Pringsheim de- 

 scribed above, will find it no easy 

 matter to make out even the termina- 

 tions of the protoplasmic threads, but 

 it is well worth the trial, as a good test 

 for manipulative skill. We suggest 

 it to those who have exhausted the 

 charms of AmpJiipleicra. 



ERRATA. 

 Page 125 ist column, line 23, the word " part" 

 should read " ounce." 



NOTES. 



— G. Volkins states that at the tip of 

 the leaf of Calla there is a modified lorm 

 of the .stomata, which assists in tlie excre- 

 tion of water by the leaf. The modified 

 stomata are larger than the others, situa- 

 ted in the epidermis of the cylindrical 

 apex of the leaf. The water is excreted 

 by pressure from the root. 



— J. C. Miiller has made some curious 

 observations on the action of a solution 

 of 50 grains of pure caustic potash in an 

 ounce of water upon living diatoms. 

 The species experimented witii was Sync- 

 dra radians. Tlacing the moist diatoms 

 on a sli]) and allowing them to get nearly 

 dry, the solution was applied when in a 

 few hours, the connective separated into 

 two fine silicious films, one part belong- 



