1138 Summers.—On the Occurrence of Lens-cells in the 
Several other species are figured by Berger in his handbook on 
‘ Mesembrianthemen und Portulaceen * (2). 
The assimilation tissue is situated under the epidermis of the side of 
the corpusculum and forms a hollow cylinder. There is none of this tissue 
under the upper epidermis. 
The above-mentioned species have been placed by Marloth in a class 
of plants which he describes as being 
provided with window-leaves (‘ Fenster- 
Blatter ’). According to him the leaves 
remain for the greater part buried in the 
ground, so that only the upper surfaces 
of these are visible. As under the 
upper epidermis water-storage tissue is 
present, while chlorophyll - containing 
tissue is completely wanting, the light, 
after entering through the cells of the epi¬ 
dermis, is dispersed and reaches the as- 
similatory tissue at the sides in a diffuse 
condition. ‘Jedes Blatt hat also ein 
Fenster, durch welches es sein Licht 
erhalt 5 ( 7 ). 
In M. truncaielluni,Y[2cwor\h ., Marloth 
found that the brown lines of the upper 
surface were due to cystolith-like struc¬ 
tures under the epidermis. These were 
filled with a strongly refractive substance 
containing much tannin, which assisted 
effectually in dispersing the light enter¬ 
ing from above. 
I have lately had the opportunity of 
examining some of these peculiar Mesem- 
bryanthemum species through the kind¬ 
ness of Professor Schinz, of the University 
of Zurich, who placed at my disposal 
material collected in Cape Colony and 
preserved in alcohol. In the case of 
M. pseudotruncatellum , Berger, I received in addition a quantity of living 
material raised from seed in the culture-houses of the Zurich Botanical 
Gardens. 
A two-year-old plant of this species is usually 2*5-3 cm * height; in 
shape it is an inverted truncated cone 2-2*5 cm * in diameter at the upper 
end. Here, also, the two leaves grow completely together as far as the 
upper surface, where they are separated by a deep slit (Fig. 1). 
* /q 
Fig. i. Mesembryanthemumpseudo - 
truncatellum : two-year-old plant. 
