126 Rhodora [May 
TABLE or HanirAL FACTORS. "c 
(The numbers refer to the synopsis of Plant formations following.) 
saline 
calcare- (/7a/o- 
Soil silicious argillaceous ous øytes) 
Humidity ub In sunlight (1) (2) ix oto MS 
slight | 
Arid Plants In shade DU hie ag 
Humidity — In sunlight (2) (o) 
medium | 
Upland Plants In shade (3) (4) + Gas aoe 
Humidity oer In sunlight (5) (6) RE 
great i 
Dist Plants (In shade (8) (8) Bow: aes 
Saturated Mos is bs sunlight (ga & 95) (ga & 95) .... (10) 
or 
nearly so Swai Plants In shade (11) (11) EE F D 
Hydrophytes rooted (12) (13) cast HD 
Submersed or 
Aquatic Plants floating (15) (15) reir T 
Special Adaptations: Dependent upon human habitation (17) 
" uU * cultivation. (18) 
Saprophytic or parasitic on other organisms. (19) 
It is probable that there are other plant-formations besides those 
here given. "There may be found a limestone formation with its char- 
acteristic species to parallel the silicious, argillaceous and saline 
series given. A sea-cliff formation (m) may occur northward along 
the coast, as a number of peculiar species are found at Nahant and 
Cape Ann in such situations. There may be a district flora charac- 
teristic of “dry open places" (n), (0), or of the upland thickets inter- 
mediate between (1—2) and (3-4), but, if so, it certainly is not very 
pronounced. In this classification, I have endeavored to give only 
those plant-formations which stand out with clearness and are easily 
segregated by their flora, recognizing the fact that they all intergrade 
with each other and that many species are common to a series having 
the same soil or the same relative amount of humidity, while others, 
like weeds, pay little regard to any of these conditions. 
The species here italicized as “characteristic” of each formation 
are those usually found here only in the given formation and occurring 
rarely elsewhere ; the other species listed are common in the forma- 
tion but not at all confined to it. By far the greater part of the flora 
