and Laboratory Methods. 2471 



Thayer, W. S. Remarks on the clinical staining. Journ. Boston Soc. Med. Sc, 1001, 



value of Ehrlich's method of examination of V, 6, o41. 



the blood. Boston Med. and Surg. Jour., 188:], Willebrand, E. A. v. Eine Methodefur gleich- 



CXX\III, 156; 182. zeitige Combinationsfarbung von Bluttrocken- 



Von Leyden. Mittheilungen liber Ziemann's praparaten mit Eosin und Methylenblau. 



neue Methode der Kernfiirbung von Blutprapa- Deutsche med. Wochnschr., Leipz. u. Berl., 



raten. Deutsche med. Wochnschr., Leipz. u. 1901. XXVII, 57-o8. 



Berl., 1898, XXIV, Ver. Beil., 144. ^^.^^^^ ^ ^^pj^ ^^^^^^ j^^ ^^^^ differential 



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schwere Anamien. Charite-Annalen, 1891. jour. Med. Research, IOOl', 2, 138-o9. Abs. 



XVI, 217. Jour. Appl. Micr. and Lab. Methods, 1902, V, 



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Massachusetts State Board of Health. ErnesT LinwooD WalKER. 



Laboratory Outlines for the Elementary Study of Plant 



Structures and Functions from the Standpoint 



of Evolution. 



THREE INTERESTING GREEN ALGAE. 



XLI. Ocdogoniiim crisp iim (Hass.) Wittr. {(E. nodosum Keutz.) Family, 

 Oedogoniaceae. 



This plant grows either upon or beneath the surface of ponds and pools, 

 usually attached to various solid objects. It fruits most abundantly during May 

 and June, and will grow well in aquaria. 



1. Mount some of the filaments in water and examine under low power. 

 Note that the filaments are unbranched and have a definite holdfast at the base. 

 Draw. 



2. Draw one of the cells under high power, showing the chloroplast with 

 pyrenoids and the nucleus. Draw the basal cell (holdfast). 



3. Nonsexual spore reproduction. If the filaments are in proper condition, 

 any cell may develop into a zoospore and escape from the cell wall. Draw an 

 empty cell. Draw a free-swimming zoospore. These have a circle of short 

 flagella or cilia. Draw a zoospore which has settled down and enlarged and is 

 developing a holdfast at the base. 



4. Sexual reproduction. Note the oogonia, large cells each with an oosphere 

 filled with food material. Draw. Find the opening at the base for the entrance 

 of the spermatozoid. Draw an antheridium, usually consisting of two or three 

 very short cells each of which gives rise to two spermatozoids. 



.5. Look for escaping spermatozoids and for spermatozoids which have 

 entered the oogonium. 



6. Draw an oogonium containing a ripe, thick-walled oospore. 



7. When the oospore germinates it divides into four cells, each of which 

 develops into a zoospore. The zoospores settle down and develop into new 

 Oedogonium plants. An attempt should be made to have oospores germinate in 



