1908] BRIEFER ARTICLES 51 
and measurement by advanced ones. Of the plants available for the pur- 
pose in winter, namely, those which are or may readily be grown or kept in 
greenhouses or houses, the best known heretofore are as follows: species of 
Chara and Nitella, which may be kept over winter in tubs under the green- 
house benches; Elodea and Vallisneria, responsive to the same treatment; 
Tradescantia zebrina or wandering Jew, very commonly grown, and T. 
virginica (or pilosa) which can be kept part of the winter if planted on a 
greenhouse bench and cut back until July or August; squash or tomato, 
which can be grown from seed in two or three weeks; root hairs of mustard 
and other plants, which can be grown to perfection in wet, covered flower-pot 
saucers; heliotrope and pelargonium, 
The brevity of this list in plants presenting material ready at all times 
led me to undertake a systematic search for others through a range of 
educational greenhouses, and I was successful in finding the considerable 
number of new cases marked by the asterisks in the table below,? I 
undertook to determine, upon a uniform system, the rate of movement, 
both for these and for the other common forms, at the two temperatures 
Practically most important, namely 20° (approximately ordinary room 
temperature) and the optimum; and the results are recorded in the table. 
For the control of temperature I used GANONG’s temperature stage, with 
the method, including standardized ocular micrometer and metronome, 
described in his Laboratory course in plant physiology. The figures in the 
table are averages of two or more determinations from different specimens 
: : r d 
€xcept in a few cases of the optimum, where onl ihc seapaeeee 
GREENHOUSE PLANTS SHOWING PROTOPLASMIC STREAMING, 
WITH ITS RATE 
NAME OF PLANT PARTS OBSERVED 
@ 20° | Optimum 
ae 
*Abuti : 
Abutilon striatum hyb. unicellular hair from surface of | .161 | .773@32° 
* ‘i : hair from calyx -016 
Ampelopsis Veitchii (Bos- | unicellular hair from under side of | .138 | .368@36° 
heed midrib 
*Azalea ‘iva (oat) root hair of seedling +322 s 
Bras es cell of hair from leaf blade -138 | -322@34 
ica alba (white mustard)| root hair 322 
"Those marked by ian asterisk are here recorded for the first ime. 
. _ 7 As concerns outdoor plants for this same purpose there is a paper entitled ““Sub- 
al for Protoplasmic movements,” by B. D. HatsTED, in Bull. Bot. Depart. Iowa 
Agric. Coll. 1888; 578. It enumerates‘ten common plants. 
