516 
several times more long than broad, rarely about as long as broad. The 
ends are for the most part rounded, occasionally pointed, irre- 
gular or more or less straight. Often oval and whetstone-shaped 
crystals are found. Once they were seen as rhombs with rounded 
sides. In a few cases the crystals showed large surfaces of indefinite 
shape, in other cases the surfaces were narrow, long and slightly 
eurved. The’ multifarious ribbon- and needle-shaped crystals that 
occur are allied to this last-mentioned form. These are generally 
much curved. Straight needles are rare. The ribbon-shaped crystals 
are often branched or split up into separate curved needles. Finally 
connected with the curved, needle-shaped crystals there are filamentous 
ones, which may be very much twisted and often form clews. The 
crystal plates often form aggregates. 
When leaves are treated with Mortscn’s reagent aggregates of 
crystals are generally formed in the cells which contain chlorophyll; 
they are composed of orange-yellow plates and red erystals resembling 
needles. 
The shape of the orange-yellow and orange crystals often differs 
in one and the same object. In the flower of Dendrobium thyrsiflorum 
I found orange-yellow (Kl. et V. 151) whetstone-shaped plates and 
orange-yellow (151) thread-like crystals, also aggregates of fine needle- 
shaped crystals coloured bright orange (101) and to some extent 
orange-red (81). In the flower of Cucurbita melanosperma I found 
thread-like erystals and very thick, almost completely straight, flat 
needles in the hairs. 
The shape of the crystals is sometimes very dependent on external 
circumstances, as for example, on the quantity of Motiscn’s reagent 
into which the object is put. In the petals of Chelidonium majus, 
for example, I got thread-shaped crystals whenever I placed them 
in a flask with a large quantity of Motiscn’s reagent, and crystal 
plates when a petal was placed in a small quantity of Motiscn’s 
reagent between a cover-slip and a slide. 
However diverse the crystals may be there is an important point 
of difference between the red and orange-red on the one hand and 
the orange-yellow and orange crystals on the other hand, namely, 
that when the carotinoids have separated out in the form of plates, 
among the former well-shaped parallelograms are nearly always 
formed and these are not met with among the orange-yellow and 
orange crystals. 
In the leaves of Urtica dioica I was able to observe that the 
quantity of the reagent may influence not only the shape of the 
crystals but also the place where they are formed. By using much 
