REVIEWS 37 



tree, and hickory. The practically extinct chestnut is being largely replaced 

 as a major member of the association by hickory (Carya tomentosa) . The most 

 conspicuous trees of the deciduous phase of the successional forest are black 

 locust (Robinia pseudo-acacia) and tulip poplar (Liriodendron), and of the 

 coniferous phase scrub pine (Pinus virginiana) and red cedar (Juniperus vir- 

 giniana var. crebra). The heath flora is dominated by Kalmia latifolia. The 

 shrub understory and ground herbage of the forest vary considerably in differ- 

 ent habitats and with differences in the developmental state of the forest. 



The annotated list of vascular plants, including 934 species (789 native) 

 and 75 varieties, forms, and hybrids, is based almost entirely on 8 years of 

 field work by the senior author at all seasons of the year. It is followed by 

 statistics and a comparison of the generic coefficient with that of various other 

 areas in the United States. This cofncient is nearly the same as that for the 

 District of Columbia. The largest families are Compositae (124 species in- 

 cluding introductions), Gramineae (97), Cyperaceae (68), Rosaceae (52), and 

 Leguminosae (49), these 5 families comprising 41.7% of the total flora. 



Altogether the work is a decidedly worth-while addition to the local floras 

 of the United States. 



S. F. Blake 

 Plant Exploration and Introduction 



Bureau of Plant Industry, Soils, and Agricultural Engineering 

 Beltsville, Maryland 



FIELD TRIPS OF THE CLUB 



April 8. The New York Botanical Garden. The first trip of the 1944 sea- 

 son was a visit to the laboratory of Dr. William J. Robbins. Dr. Robbins 

 explained that his was not a teaching laboratory nor a research laboratory 

 in the ordinary sense but a laboratory for the investigation of certain vita- 

 mins and antibiotic substances. In both of these researches the unit of sub- 

 stance is very small, ordinarily the gama or microgram. We were then 

 shown a reproduction of the sort of situation which Dr. Fleming observed 

 and which started the investigation ultimately leading to the discovery of 

 penicillin. A pure culture of PeniciUum notatum was shown. The behavior 

 of various bacteria in its presence was pointed out. Other fungi being 

 tested for antibiotic substances were displayed. Dr. Robbins demonstrated 

 the method of titrating the medium for potency after growing an organism 

 in it. 



Mrs. Annette Hervey demonstrated the use of an automatic pipette in 

 transfering cultures aseptically. Dr. Roberta Ma conducted the group 

 through the cold room where organisms are cultured at the constant tern- 



